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; • User Number • Service Number
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. You will need to use a Service Number to enable Cloud PBX Auto Attendant, Online Call Queues, or dial in telephone numbers for PSTN Conferencing. Please keep this in mind, if you are porting telephone numbers to Office 365, and they are meant for your Cloud Auto Attendant, Call Queues or PSTN Conferencing, ensure to specify that this number is meant to be a service number.
Each customer has a limited set of service numbers they can request by default. 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. So if cannot request new Service Numbers, please take a look at the existing PSTN Numbers you have, to see if you have not already reached the limit.