No Internet Connection Despite iPhone Indicating Sufficient Cellular Signal

I have this problem on both my iPhone XR and iPhone 15 Pro. My phone shows great 3-4 bar LTE/5G signal, but refuses to send or receive text messages, or connect to the internet. We have an unlimited plan, so we are not being rate limited. My only solution is to use WiFi. I have tried the following:

Resetting iOS

Resetting iOS Network Settings

Converting physical SIM card to ESIM

Reinstalling ESIM

Contacting Apple support
Enabling data roaming