Hello samc4410,
Thank you for using Apple Support Communities! I understand that the network icon in the status bar on your iPhone is not updating from 5G E to LTE after traveling to an area that was previously LTE only. The network status is provided by your carrier, so you may ultimately need to reach out to AT&T for additional assistance. I would be happy to help provide additional suggestions you can try first.
Let's start by checking if you have a carrier settings update available:
Update your carrier settings on your iPhone or iPad - Apple Support
If there's no available update, or the status doesn't change after installing a carrier settings update, you may want to consider resetting your Network Settings. This resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you’ve used before. You can find that from Settings > General > Reset > Reset Network Settings.
If your signal does not update after trying these steps, I suggest reaching out to AT&T. You can also view more information about the 5G E signal here:
5G Evolution: What it Means for You - AT&T
Cheers!