No Service and Searching. IPhone 3GS

Yesterday my phone would not get any service even if I was in a serviced area. The morning I had it, it was working fine. I gave my phone to a friend so he could replace my battery. I got it back and he said he couldn't replace it. When i got it back i could not get any service. I checked to make sure what he did and all he did was unscrew the screws and put them back. I've tried putting it on airplane mode and resetting the networks and checked if I needed to update but nothing works. I put it on 3G mode and it only went to one bar, sometimes 2, and once 3, but now it has no service at all. I really want to fix it because my iPhone is broken enough lol. Any suggestions?

Added (1). yesterday morning*

Did you connect to Wi-Fi and set the date to current. After that turn off your phone and power it back on to see if it helps. Also is ribbon no 7 attached firmly to the logic board. Ribbon no 7 is the connector that connects the cellular antenna to the logic board. If that does not resolve your issue there's another problem. On the right bottom of your logic board there's a black sticker which says (Do Not Remove or something in those lines). If that's peeled off revealing a screw then chances is your friend tried to remove the iPhone 3GS logic board. If that's the case then on the bottom right is there a small gold piece still intact to the logic board. If not then that's the problem to why your phone is not getting service. That gold piece is used to ground the phone and help improve cellular antenna reception. Also you can do a restore and see if it helps.

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