Managing sound and video settings during Teams meetings and calls for optimal communication
I had this same problem and found a temporary fix - at least it worked for me. You can right click on the volume icon on the right of the taskbar and open up the volume mixer. Then, assuming the call sound is still playing and you're in a call, you should see two separate Teams volume bars/selectors (I dont know the actual term) - one with the ringtone thats going and one with the sounds in the call (people talking, etc.) You should be able to drag down the volume selector for the ringtone that won't stop and still hear your call.
This fix also worked for stopping the noise while not in a call and not actively using Teams. I think doing all of this also stops the ringtone when you are actually receiving a call, so watch out for that (unconfirmed). Hopefully it works for everyone who's been having this issue. I'm still trying to find an actual solution...