Pixel 3a XL with US AT&T (3G shut down)

I have a Pixel 3a XL that had /e/ 1.0 on it, but it would not dial out. So I was going to try the solution from the Motorola XT1965-T and reinstall the stock ROM, and afterwards reinstall /e/. But I ran into a problem. The Stock Android 11 also does not call on the ATT network. I have to upgrade to Android 12L to be able to dial out. (And it looks like it has Wifi calling but I did not try it.) After having upgraded to Android 12L, I put back the stock Android 11 ROM and again could not dial out.
My understanding is that the /e/ version for the Pixel 3a XL is “R” and should not be flashed on a device that has Android 12 or 12L. Is that correct? And if so, is there another fix to the dialing when 3G is shut down? US T-Mobile is shutting down 3G July 1st, I believe so it is getting really important in the U.S.

Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone

Yes, that is correct.

The position with 3G in USA is hard.

I think the best that USA users can do is to keep trying to share 3G success stories here.

Any initiatives to help make the success stories more easy to search on the forum would be helpful! Perhaps #3g-usa added as a hashtag to threads would work?