No service after screen replacement

I dropped my phone and got the screen replaced. I went out of town and stopped getting service and when I came back to my hometown I figured it would start working but it has not. It just says "searching.." or no service. I have tried Hard resets a lot, I have gotten a new SIM card twice, I went back to the place that fixed the screen and they were clueless. I went to AT&T and they did not know what to do but told me to go get my lower antenna replaced. I did that and it still did not work. I can connect to wifi but I can't access my data or get a signal. What parts could have been damaged during the screen replacement to cause this? I have had screens replaced by this place before and they did a good job but I am assuming them messed something up this time. They rushed through it so I don't know what's wrong. Let me know if there is another part that could fix it! I know it's nothing wrong with the SIM card, it's properly activated and I've tried SIM cards from other lines that I know work and it did not fix the issue. Thank you!