Teams, like any voice service, can get unwanted or spam calls. Unfortunately, due to the sophistication of some spammers, there is no magic fix for stopping unwanted calls. The Teams voice support team is limited in the suggestions we can provide clients because we face many of the same obstacles in prevention. 

Spam calls are hard to stop because they can come from different numbers every time, or even spoof university numbers to prevent being blocked. If you are receiving unwanted calls, our first suggestion is always to try to block the number(s). This can be done by going to your Teams call history, selecting the ellipses (...) next to the call, then selecting block. This can only be done for external callers. Internal users cannot be blocked like this, and if the spammer is spoofing an internal number, you may not be able to block it. 

We will only recommend your department request to change your university phone number in the most extreme circumstances. This is because there is no guarantee that your new number will be immune from getting spam calls, either. We will only make this recommendation based on consultation with the affected end user or their local IT support. Teams support will not rotate a user's phone number repeatedly due to getting spam calls if changing numbers does not provide results. There may also be instances where changing the phone number is not viable, because it is a main department line, or is advertised in numerous places.