Question [Q] Phone dialing but wont ever connect to call, full bars

Guys i desperately need some help...i have tried everything i can try....My S3 I747 is having a very weird problem, i am currently using straight talk...i am able to make calls with full bars indicating but all the phone says is Dialing it will not connect to the person i am calling, i have tried different roms, downgrading baseband, upgrading baseband...i finally just ended up with 4.4.2 stock rom with root, and still the same problem, the phone is unlocked as far as i know and it does detect the sim card this is my first post on XDA, but have been a user for years....PLEASE help!

Also it says AT&T in top left corner never HOME, i have had this phone for a year now, and it just started doing this out of the blue...

Has anyone else had this problem?...