No internet

I have a iphone7 and iphone11. Both are on contract sims with smarty. I have never reached data capacity in over 3yrs.

My iPhone 11 does not connect to the internet on 4G but works fine with WI-FI. If I tether through my iPhone 7 it works fine via BlueTooth.

I took my 11 to Apple and they say there is no issue with the phone.
This problem has only recently started (past 2 wks).