Need assistance/guidance to migrate a customer to SfBO with Cloud PBX


Hi Experts,

One of our customer in the progress of migrating a customer from traditional telephony to O365 PSTN Calling.




1. Why we can`t pre-configure the actual numbers without transferring them from the current telco to MS.

2. Do every user need a LineUri to make phone calls?
3. Why we can`t add communication credits
4. Why does every users needs a dedicated number? Skype for business on-premise does not have this requirement.


Any pointers would be of great help.

Many thanks!!



6 Replies

When you do porting to Microsoft from your telco the number are available to assign before the porting date/time. So you can assign them to the users. For Service numbers this is not available at this moment. After the actual porting Microsoft can change User numbers to Service numbers, will take +/-40 minutes.

I'm not sure if you need a lineUri for the users to call, you definitely need a Domestic or International and the Phone System license.

You will need to add the communication credits via Billing > Purchase Services > Communications Credits. Make sure you have Phone System enabled with licenses.

Thank you very much, Erwin.


Let me pass on this to the partner.

Hi Erwin,


Regarding the 2nd question, customer looking for more clarity.

2. Do every user need a LineUri to make phone calls?

  • Yeah licenses I understand, but I don’t understand why I have to assign each individual user a LineUri to enable PSTN calling outside. Most of our customers only have 1 – 10 numbers all users are behind a Voicepolicy with suppressed number. But Online (o365)I have to acquire more numbers.

Please help. Many thanks.

Tested this out on my own tenant, if a user does not have a number you will get the message: "You're not setup to use this calling feature, please contact your admin" when dialing out.


So it look's that you will need to have a Number for every user.



Thank you very much for your testing. It looks like product limitation.


Thanks again for confirming.

On the subject of every user needing a LineURI... this is true.  However, you don't have to only use your ported numbers.  Since you need to purchase a PSTN calling plan for each user anyway, you can request new numbers from Microsoft and use these instead for most users, they come with the license.  Then you can set up an outbound caller ID mask to look like your main number, which would be assigned as a service number.