iPhone 4s unable to connect via 3G
I have a BYOD iPhone 4s that cannot connect via 3G. It works fine on wifi. Whenever wifi is turned off or unavailable it will send texts but when a call is attempted, you receive an error that states "Call failed" "Reason was: IO error". This phone used to be on another account and worked fine when initially activated but prior to switching the account and since it has had this issue. I have tried doing a complete network reset and using the ##clear# and ##update# commands. Need assistance to resolve this issue.