I've had this issue for a few years and MS has not fixed it. I was able to do the common fix which was to reduce the Teams volume in the App Volume and device preferences setting (I had to go down to 8 to make it listenable without hearing damage). This was a workable fix. As long as my computer was not restarted, it would remember that setting for each call and Teams wouldn't override.
Now, with "new Teams", it does not remember. Every single time I rejoin a call, it will push the volume back up to 100% which is at a damaging level for me. It's been years and it's time to address this MS. I can't believe it hasn't been as many organization such as mine have users utilizing Teams for calls and meetings.