I just had this issue and solved it! All you need to do is, when you're on a call (whether it's MS Teams, Zoom, or Ring Central), turn the volume up by using the stem on the AirPods. If you don't know how to do this, you can swipe upwards on the front side of the AirPod stem. I would recommend turning this all the way up. You know when it's at 100% because you'll hear a higher pitch noise than when you are just increasing the volume. Then, change the volume on your computer to the appropriate volume.
I think this is happening because there are two volumes. The first is a master volume that's used when you aren't in a call. The second volume is only used when you are on a call, but it is layered under the master volume. So if the master volume is really low, no matter how high you make the call volume, it can't make up for the master volume being really low. The issue arises because the AirPods can only adjust the master volume, which is hidden when you are on a call.