iPhone14 IOS 17.5.1 calls keep failing

Any recommendations on how to fix? I have an iPhone 14 and IOS is up-to-date with v.17.5.1.

PROBLEM: Calls keep failing, call quality inconsistent.. this started beginning of the month. I recently changed service providers.

I have:

1) restarted the phone

2) checked for IOS updates - mine is up to date

3) toggled the airplane mode

4) removed and reinstalled the card

Only things left to do is change cell phone provider or switch to Android. HELP!