Hi, I bought a Galaxy S3 (SGH-I747M) about a month ago, and I've had a lot of connectivity issues. Previously, I had a Galaxy Ace II and had no problems for over two years. Randomly, the phone will lose connection to the network. I still get full bars on the notification area, but I can't place or receive any calls. The phone will ring, but if I try and answer the call will immediately drop with a "Call ended" message. Likewise, if I try to call someone, the call immediately drops with the "Call ended message". If I go in settings -> Call -> Additional settings I get the "Network or SIM card error" message. I have tried the following things MULTIPLE times, so please don't suggest them to me again: 1. Rebooting the device. This usually fixes the problem temporarily, until it eventually happens again. Sometimes multiple reboots are required. 2. Set the phone to airplane mode then out multiple times has no effect. 3. Taking out the battery for an extended period of time has the same effect as rebooting would. 4. Taking out the SIM card and replacing it. 5. Cleaning the contacts on the SIM card. 6. Restore the phone to factory defaults. 7. Do a hard reset on the phone that erases everything back to factory default. 8. Disable GPS/Bluetooth/Wifi for an extended period of time. 9. Disable data on the phone. (My plan already has a data lock). 10. Update to the latest firmware with Samsung Kies 3 and OTA. Current firmware is PDAMK5/ Phone:MK5 /CSC:MK5 (KDO). 11. Force the phone to not use LTE, such as WCDMA. Phone is running Android 4.3. This is getting ridiculous. My wife is pregnant and I need to be able to take calls at all times without having to do some voodoo magic on a brand new phone. Anyone has any idea what to do next? Edit : I can send and receive text messages while the problem is going on.