Changing carrier and phone not working with new SIM
I have been using ATT service on this i777, now going to China and will be using their carrier for a long time. I learnt I have to go to either China Mobile or China Unicom if I'm to stick with this device. However both carrier's SIMs resulted in "SIM card not provisioned" notice and it's not working.
I am wondering if calling ATT helps, or I need a SIM unlock code, or I have to install a custom ROM to somehow bypass the SIM check? Or even more? I love this phone so I don't want to buy a new one here in China.
Any help is greatly appreciated!!
Sent from my SAMSUNG-SGH-I777 using xda app-developers app