No Service, SIM Card checks good (replaced new with new one)

I recently had my iPhone 7, 128GB start to drop service and remain in search. I performed a Forced Reset and that corrected the error. Days later it came back and the Forced Reset did not work. I re-seated the SIM Card and the error disappeared. A few hours later the Service dropped again and nothing has fixed it.

I went to AT&T for a new SIM Card and that did not work. I Reset Network Settings and that has not worked. I have toggled all other options such as Cell Network, LTE, Roaming, Airplane Mode, etc. , all with the same result of still No Service.

I have not attempted to do a full restore I will try that tonight, but if that doesn't work, what needs to be replaced? I am willing to repair it myself, please help!!! :)