For those of you that have ever requested a new PSTN Number in Skype for Business Online, you have noticed that you can actually request 2 types of numbers:
So when do I need which number?
Let’s start with the User Numbers. User Numbers are telephone numbers that you can assign to any of your PSTN Calling users. They are regular telephone numbers so this means you can either port your existing user telephone numbers or request new ones. These telephone numbers are meant for a single user to receive and place calls. If you are looking for a new telephone number to assign to your PSTN Calling users, this is the one for you.
Service Numbers are a bit more special. Service numbers are meant for a large number of incoming telephone calls at a given time. You will need to use a Service Number to enable Cloud PBX Auto Attendant, Call Queues, or dial in telephone numbers for PSTN Conferencing. Please keep this in mind, if you are porting service telephone numbers to Office 365, and they are meant for your Cloud Auto Attendant, Call Queues or PSTN Conferencing, you must manually submit a port order request.
Each customer has a limited set of service numbers they can request based on number of relevant licenses they have bought. Should you need more, you can use the Office 365 Admin Portal to request more Service Numbers.
One thing to consider is that when you enable PSTN conferencing, Service numbers will be used to enabled this feature. This will use your existing limit of Service Numbers you can request. The details on how many service numbers can be acquired, please refer to Getting Skype for Business service phone numbers.