Changed the battery on my wife's 6s, and now she has "no service" mess

I reopened the phone, checked the battery and surrounding connector, the antenna lead and it’s connector, and all seem to be connected fine. Now I hear that T-Mobile, our carrier through Consumer Cellular, are making major connector changes through February, and our cellular signal is affected by this. I contacted CC and they are sending AT&T SIM cards for both of our phones. I’ll try those along with using WIFI calling in our home (which works well) to get through this. I tried to make a Genius Bar appointment through Apple, but all the site gives me for support is Target, and Best Buy stores, not even the one Apple store which is located in Brea, CA. This is all due to Covid-related issues. Not sure what to do next, but her new battery (from iFixit) is working fine.

I had to take the iPhone to a repair center. They told me one of the issues was a chip on the logic board which went bad. The other issue was a flex-cable on a new screen which I just purchased from iFixit and installed. I'll check the parts warranty on that item.