Hey guys, hopefully I'm not too late and this can help many others. I had the exact same problem. Replaced my screen and then had problems with No signal, stuck in roaming, emergency calls only.. What I did was with the phone still turned on I took the back cover off (pulls off a lot easier from the headphone jack). With the cover off looking at it from the back, there are 2 terminals on the top right (to the right side of the camera) you must take a screwdriver or any conductive metal and touch the 2 terminals together for about 10 secs (you will see the signal strength come back on the notification bar. That will act as an antenna and jump start the reception. Test it out for a minute or so and if all is good, put the back cover back on and you're all set. Hope this helps and works for the rest of you, worked for me!