Thank you for all the information about what is going on and all the steps you have tried. You have tried some excellent troubleshooting steps, which lead me to believe it may be an issue with your cellular connection rather than an issue with your receiver on your iPhone.
I found an article with steps to troubleshoot this, and you can skip any steps you have already taken:
Thank you for posting in the Apple Support Communities.
Thanks for the response! It happened again yesterday... It seems to be happening more frequently in the past few weeks now.
I checked the link and have tried all of the things listed at one point or another over the past few months. I did just check my Carrier settings and it said it had updated (it's on 14.1), but I am not sure when that happened (could have been today, could have been after my last restore last week, not sure). I'll keep my fingers crossed that maybe that fixed it...
If it continues to act up, would you recommend that I bring the phone in to an Apple store or an AT&T store? I bought the phone through Apple, but my carrier is AT&T (and if you suspect that the problem may be with the cellular conection), maybe the AT&T store would be the better choice?
I really wish the problem would be more consistant or go away, cause trying to get the problem solved is driving me crazy!
I definitely understand your frustration with this issue, especially since it is not consistant. You may want to go ahead and reach out to AT&T first since step 9 in the article recommends this:
9. Contact your carrier to:
- Verify that the iPhone is properly set up on the account with the appropriate, current data plan.
- Verify that there are no account-related blocks.
- Find out if there are specific error messages in the carrier logs that could help determine why the issue is occurring.
All the best,