Hi DeeJ250,
Thanks for contacting Apple Support Communities!
We understand that your iPhone display stops responding while you're on calls.
If you have a screen protector or case on your iPhone, you may consider removing them to test the display as outlined here: If the screen isn't working on your iPhone or iPad
"If your screen is too sensitive or responds intermittently to touch
- Restart your iPhone or iPad.
- Make sure that your screen is clean and free of any debris or water.
- Disconnect any Lightning or USB-C accessories. If your screen works after removing an accessory, try using a different outlet, cable, or charger.
- Remove any cases or screen protectors."
If you still experience the same behavior, you may also consider reaching out to Apple Support directly to investigate this further as your iPhone may require service: Contact Apple Support
Take care!