iPhone 6 keeps searching for signal

okay so, my iphone bended exactly one year ago.... and ever since it has been searching for signal.... sometimes i was lucky and the service came on, for like a day or two, but then it started searching all over again....

I have tried everything by now exept switching the internal antenna.

i have searched the web, for days, and i have found a lot of solutions, but none which worked for me.

any suggestions? i'll do anything by now....