I've been having a problem recently that i'm rather stumped about, i've been trying to fix it for the past few days, looking pretty much everywhere on the net for a fix but this is pretty much a last resort before i take it to a random shop and have them attempt to fix it.
So basically i had a galaxy S3, it broke and a close friend of mine had one sitting around gathering dust so he gave it to me to use. The problem is that for some reason this phone refuses to get any mobile signal. It connects to my WiFi without issue however it always has no service and says it can only perform emergency calls. At first i figured it may have just been my SIM card so i've tried it with 3 different SIM cards with 3 different network carriers (I've been informed that the phone is definitely network unlocked too) i've tried to manually connect to the network through the mobile network settings but that seems to bring me no luck either. The phone was rooted and whatnot but i've attempted to flash a stock ROM onto it to see if it was a ROM issue but that seems to have done nothing to help. Now i'd consider myself rather tech savvy but i'm a novice when it comes to tinkering with mobiles so any help or advice you guys could give to possibly resolve my issue would be greatly appreciated.
After writing this and performing one last search so that i don't make a complete fool of myself i've stumbled upon modem flashing so this may be something that i attempt but i'm currently trying to figure out how it all works. If you need any more information i'll happily get back to you as quickly as i can.
Quick things to close up to save time: It's running 4.3. It has an IMEI number matching that on the box. Everything else on the phone working 100% just not able to get mobile signal. Not currently rooted.