THL android wont allow number to connect

i bought a THL phone off of ebay. i purchased a 4GEE pay as you go sim to go with it. the problem im having is that voice and text messages cannot be sent or recieved. i set up the sim card on an iphone and put it back in the THL. i can connect to intrrnet using my service providers data plan. my phone shows signal full with purple bars but the phone number is said to still not be connected when called. Is this a hardware issue? May have the phone been partially blocked by a previous owner? I've contacted the seller however thy arebt much help. The only thing i can see on the phone is that the superuser binary needs updating. And fails every time i try.

Any help will be greatly appreciatedt thank you