Hi everyone, a few months ago I bought a galaxy s4 I9505 and unlocked it via unlock code. I did this immediately on first boot. Everything worked since I had a hardware problem in which the blue LED was on all the time. The phone is under warranty so after 3 weeks I got the phone back from service. They told me they have changed the motherboard and that everything is working right now. After turning the phone on I had to put in the unlock code again because it said sim locked. This was successful !!! Now I have no signal indoors end very poor signal outdoors. I tried factory reset and hard reset a few times but it didnt work. Even under a small roof I have no signal at all and I cant make any calls or texts. I tried different sim cards of other operators but no luck ! My question is: could it be my fault because I put the unlock code or is hardware related so I should give it back to service (which is frustrating) ? Thanks for your help !