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Number porting 101 – Transferring phone numbers to Microsoft

Let’s say you are thinking of moving your phone numbers to Microsoft. Great! However, there are a few things that you need to take into consideration before making this leap. In this article I’ll go over what number porting is, what challenges you may face, and what you’ll need to know to get your numbers ported! So buckle up, because it may not be as easy as it sounds!

Caveats of number porting

First things first, I won’t come right out and say number porting is a simple process. It can sometimes be a daunting task, but this all depends on how your carrier regulates things. The PSTN (Public Switch Telephone Network) is a tricky beast when it comes to rules and regulations for PSTN calling. I say this because with the PSTN being a legacy service, it introduces all sorts of complexities due to service providers (AT&T, Frontier, CenturyLink, etc.) not knowing what/how to regulate your calling services. I’d like to quote Korneel Bullens of Microsoft, when he states his take on PSTN’s third law: “For every regulation, there is an equal and opposite regulation”. Although quite hilarious, he basically means that what may work for customer A in terms of porting may not necessarily work for customer B even if they follow the same process. All that said, be prepared for a plethora of different scenarios from one carrier to the next and know that mileage may vary on what they require. Great, now that we have laid the foundation for some quick caveats, lets get down to the real details on what number porting is, how to overcome some number porting challenges, and learning your roles in this entire process.

What the heck is number porting?

Let’s say you own a bunch of phone numbers with a telephone company whether it be (AT&T, Frontier, CenturyLink, etc.) and you want to transfer those numbers over to Microsoft. Well you would go about this by porting the numbers from one carrier to the other. What if you only want to transfer a small subset of numbers though? No need to worry, Microsoft still has you covered, as they allow a partial port where you can select a subset of DIDs (phone numbers) to transfer over to Microsoft from your old carrier. Also, although not very common you do have the option to port out, meaning you can port your numbers away from Microsoft to another carrier if need be. Great now that we know what porting is, let’s discuss where you can do your porting with Microsoft. You can port your numbers to Microsoft in any of the following countries (as of November 2018):

  • Belgium
  • France
  • Germany
  • Ireland
  • Netherlands
  • Spain
  • United Kingdom (U.K.)
  • United States (U.S.) & Puerto Rico
  • Canada
  • Australia (through partner)

Note: According to Microsoft, number porting, in general, requires the availability of Calling Plan (PSTN Calling) service in that country

Great! Now that we know what porting is and where we can port, let’s discuss what types of numbers you CAN and CANNOT port.

What numbers can I/can’t I port?

You CAN port (pretty much anything that makes your phone ring):

  • Landline phone numbers
  • Mobile device phone numbers (US and Puerto Rico ONLY)
  • Toll phone numbers
  • Toll-free (except for UIFN)
  • Service phone numbers
  • Fax phone numbers (transferred as a subscriber number, thus cannot be used for faxing)
  • VoIP phone numbers
  • EU Non-geographic numbers

You CANNOT port:

  • Phone numbers used for data connections
  • Phone numbers dedicated to faxing

In addition to what is mentioned above you need to take into consideration the types of number ports mentioned earlier.

  1. Full Port – Transfer all numbers in your BTN to Microsoft
  2. Partial Port- Transfer only some of your numbers in your BTN to Microsoft
  3. Inter-tenant Port – Transferring numbers from one O365 tenant to another. This involves port-out and port-in, thus port-out PIN must be set (US Only)
  4. Project Port- Having multiple port orders with a tight schedule. This involves multiple service providers or multiple accounts. In addition, this may involve fragmenting numbers and their associated services

Note: In the US, if the number ported is the BTN, a new BTN with the existing service provider must be assigned

Now that we know what can and cannot be ported let’s go over some of the challenges you may (but hopefully won’t) face when porting your numbers to Microsoft.

What are some challenges I may face when porting?

Unfortunately, not every port will go smoothly. With that said, it’s always good to understand what challenges you may face when planning a port and how mitigate those challenges. Some of the most common issues revolve around:

  • Global porting is often governed by regulatory bodies
    • As mentioned earlier, for every regulation there is an equal and opposite regulation. Meaning your port regulations typically vary by country and port type.
  • Level of regulator influence for porting processes, SLA’s, & disputes varies by market
    • In many cases the losing carrier will tell you they can meet a deadline to port (i.e. 3 weeks). However, if they decide the morning of the port that they can’t transfer over your numbers and cancel the port order, there are no repercussions on their behalf
  • Some port types are not regulated
    • For example, complex ports with multiple carriers can cause a significant delay in the porting process while agreements between the two service providers are hashed out
  • Some port types are not even supported
    • Fragmenting phone number ranges is restricted in many markets thus restricting you from moving your numbers to Microsoft
  •  The current service provider frequently misses the SLA
    • Unfortunately, the losing carrier often doesn’t face any type of penalty for missing the service line agreement
  • Expediting ports is outside of their process
    • For the carrier the exact opposite almost always happens. When the losing carrier needs to expedite the process they will go and look for someone that can handle this request “quickly” but often finding someone to do this process takes longer than the typical port time itself
  • Porting complexity
    • Sometimes the SLA could be depicted as being written in a different language since you nor the losing carrier of that SLA can even clarify why they can’t port a number
  • The losing carrier
    • As you may have noticed before the current service provider can also be considered the “losing carrier” since they are the ones losing business from you! Since they are losing business they will try to make you jump through as many hoops as possible to delay transferring your numbers over to another service provider (evil right?)

What are some common mistakes with porting?

Just so you don’t give the losing carrier more fuel to add to the fire in delaying your port, you’ll want to take note of these common mistakes:

  • Mismatched account information
    • By far, the biggest mistake we with customers at Perficient is them not knowing or providing incorrect account information. Without correct account information (i.e. authorized name, address, account number, BTN) the losing carrier will shoot down your request right away. Or even worse yet, they can sit on the incorrect information you provided them for weeks and then deny the port order form shortly before your port order date. Then guess what? You get to start from step 1…. all…over….again….
  • Advanced call control features are not disabled
    • Hunt groups, distinctive ring, etc. if these are left enabled this blocks them from being ported. The losing carrier typically takes 6-8 weeks to inform you of this. Guess what? Yep you guessed it, back to step 1!
  • Numbers in the port request come from multiple carriers and accounts
    • This is a BIG NO NO! To stay away from this, just remember to stick to 1 port range from 1 provider every single time you submit a request.
  • Disconnection with existing service provider
    • Yep you read that right, DO NOT just call up your existing service provider and tell them “I don’t want my services with you anymore, just cancel all of my phone numbers”. This is effectively a death wish, since you’ll go to submit your port order with those numbers and guess what? You don’t own those numbers anymore since you just told your existing provider to cancel your services with them thus there is nothing to port!

Microsoft takes 90% of the frustration out of this entire process, all you need to do as a customer of Microsoft is ensure you provide them the correct information (hopefully the first time).

How long does porting take?

According to Microsoft the SLA for processing and scheduling phone number ports is generally around 7-14 business days. However, it can take up to 30 days (or in rare cases even more) depending on the current service provider.  In terms of port activation this follows a universal process that takes about 2 hours to complete. Lastly, for number conversion and inter-tenant ports this can be completed within 1-3 business days. 

How do I submit a port order?

There are two ways to submit a port order:

  1. Automated Port – Done in the Skype for Business Admin Center, can only be used in the US, and plan to port less than 999 phone numbers in that particular port order
  2. Manual Port- Done via email, required for all other markets, and if porting more than 999 phone numbers in that particular port order

What information do I need to know for my port order?

You’ll need to meet the following prerequisites to ensure you have a successful port:

  • Recent telephone bill/invoice
    • Includes: Account number, BTN, Billing Address
  • CSR (Customer Service Record)
    • Includes: Service address and list of numbers belonging to BTN
  • LoA (Letter of Authorization) – Different form per country and per type of number
  • [RECOMMENDED] – It is highly recommended to verify with Microsoft that the numbers can be ported.
    • Submit a service request/ Email to: (US and Puerto Rico) or (Europe)

What if I have a huge complex port?

Fear not my friend, you have Microsoft to help! For more complex ports involving multiple port orders with a tight schedule, create a service request to initiate a project port. 

Note: When planning for site migration to Calling Plan you will need to account for number porting timelines. A full-port is often preferred over multiple partial-ports. 


Now that we have covered all parts of a port request hopefully you have the right knowledge to guide you through your future ports. As a final takeaway, ALWAYS make sure you do the following:

  • Complete your LoA correctly
  • Verify with Microsoft if the numbers can be ported (
  • Double (or even triple) check that the port request contains the correct information
  • If you are expecting to work on a complex port with multiple port requests, involve the port project team as soon as possible
  • Leverage relationships with your existing service providers, as this could help you when it comes time to port 🙂
  • Acknowledge the risk that project timelines can slip due to exceptions or industry actions. To mitigate this risk, you should always provide multiple port activation windows and work with your stakeholders to manage expectations of this porting process.

That wraps up all the pieces of the porting process and what things you will need to consider before you start. I hope you have found this article helpful and I hope you’ll check back soon since I write various articles on all things Skype for Business Online and Teams. With all that said, I’ll see you in the next blog article!



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Brian Siefferman

Brian is a Technical Consultant for Perficient’s Unified Communications practice focusing primarily on Skype for Business and Microsoft Teams workloads. He has been in this role since December 2017 and has an active presence blogging about all things Teams related. Currently, Brian resides in the suburbs of Chicago and enjoys running, swimming, weight lifting, and playing soccer in his free time.

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