PROBLEM RESOLUTION:
It's not a carrier problem. I changed to T-mobile from AT&T and the problem followed. It's not a sim card issue because i went through 4 esims and 2 physical sims. Samsung has told me repeatedly that it's not a phone issue, when it obviously is. They were adamant that it was a carrier issue and would not even listen to me explain what was happening.
Yesterday, after 2 months of frustration. I decided to try a factory reset and that seems to have fixed it (for now at least). So here's what you need to do:
Backup your phone first!!! Go in to the bootloader (hold the power button and down volume button until the screen turns black. While still holding the power button, slide your other finger from the down volume to the up volume. After a few seconds the Samsung logo will appear. Release all the buttons and the bootloader menu will pop up. Wipe the cache, do a factory reset, and reboot it. Do a restore and you're done. My phone wouldn't connect at all, would show me connected to other networks (like sprint or ATT) or if it did connect to T-Mobile, it wouldn't stay connected for very long and I could only make emergency calls. After doing the factory reset, its been connecting and staying connected. I can now make and receive calls and texts without issue.
Hope this helps
