In Microsoft Teams, only one phone number can be assigned to one user at a time. However, you can use a trick to get around this restriction for incoming calls.
If your SIP provider supports it, you can set up call forwarding from a phone number or an extension of a number block to the number associated with the Teams account. For inbound calls, this allows you to bundle multiple phone numbers to one user.
If you use a number block with easybell, you can outsource individual extensions yourself in just a few steps and then configure them with such call forwarding.