-Run the Set-CsPhoneNumberAssignmentcmdlet and specify the -PhoneNumberparameter:
The dial pad in Teams only appears when a user is enabled for voice services and has a phone number assigned. In the output, there is no phone number assigned to User1 (OnPremLineURI is either not set or false). Running the Set-CsPhoneNumberAssignment cmdlet with the - PhoneNumberparameter will assign a phone number to User1, enabling calling functionality and making the dial pad appear in the Teams client.
-Assign a Microsoft Teams Phone Standard license to User1:
The user must have the appropriate licensing for Teams Phone services to enable the dial pad for making calls. From the output, it is unclear whether User1 has the necessary Teams Phone Standard license. Without this license, the calling features (including the dial pad) will not be available. Assigning the license ensures that User1 can make and receive calls in Teams.

https://docs.microsoft.com/en-us/microsoftteams/change-the-phone-numbers-on-your-audio- conferencing-bridge

A: Change the default phone number of your conference bridge (optional).
The default phone number of your conference bridge defines the caller ID that will be used when an outbound call is placed by a participant or the organizer from within a meeting.
Only a service toll number can be set as the default number for your conferencing bridge; service toll-free numbers can't be set as the default number of your conferencing bridge. If you are assigning a service toll number and you would like to set it as the new default number for your audio conferencing bridge, perform these steps:
1. On the left navigation pane, go to Meetings > Conference bridges.
2. Highlight the service toll number that you want to configure as the default.
3. Select Set as default.
B: Note: In addition to getting phone numbers for your users, you can get toll or toll-free phone numbers for services such as Audio Conferencing (for conference bridges), Auto Attendants, and Call Queues (also called service numbers). Service phone numbers have a higher concurrent calling capacity than user or subscriber phone numbers. For example, a service number can handle hundreds of calls simultaneously, whereas a user's phone number can only handle a few calls simultaneously. To get service numbers, contact your operator.
Reference:
https://docs.microsoft.com/en-us/microsoftteams/change-the-phone-numbers-on-your-audio- conferencing-bridge