Verify your account -- Could not confirm verification

I am stuck in GroupMe H3LL!

I am attempting to login using my email and password and I am getting an error that reads "Your phone number is no longer associated with this account. Enter a new phone number to verify your identity." and then "Could not confirm verification."

I have tried:
using my email to login.
using my phone number to login +1xxxxxxxxxx. (I've tried every possible format.)
resetting my password.
clearing my cache.
connecting to a different network.
disconnecting from VPN.
both web and mobile app.

Nothing is working!!!

I've now made three suport calls -- and have spent a total of 2+ hours with a MS live chat support session.
They are sending me in circles.
They then say they'll escalate to Engineering and get back to me, but they don't ever get back to me.

The web version was working for a while and I was only having the issue on the mobile app.
Trying to fix the mobile app issue, I think I may have created a glitch.
I don't recall exactly what happened because I've been turning in so many circles.
I may have changed the phone number associated with my account (while I was able to login to the web).
Or I might have attempted to login via Apple in the mobile app.
I seem to recall getting an Apple pop-up asking whether I wanted to change my phone number -- I clicked Yes before realizing what was happenening.
Then it kicked me out of everything -- and now I can't login at all via web or via mobile.

Uggggggghhhhh!
I'm the administrator for several groups and I can't login.