@totalsonic Didn't know about the July 1st thing. I believe that the booster acts as a proxy server. I do know that without it calls in or out do not work.
Edited my first post.
EDIT: AT&T 3G shut down Feb 22
T-Mobile will shut 3G down July 1st and Verizon probably in Dec.
EDIT: 3/6/22 OPO sim disabled. XperiaX and Pixel 3a still good.
EDIT: 3/15/22. No more calls in or out Pixel 3a or Xperia X. So much for high hopes.