I have tried other sim cards and its not that. Messages like "IMS keeps stopping" and "Phone keeps stopping" are a problem with models bought in one country and used in another. It prevents your phone from working properly and Samsung is not doing anything to prevent it. Their customer service is horrible and cannot seem to help. After calling 5 times during a month period and talking to "tier 2" engineers, I just decided to not use their brand anymore. Its a great phone when its working, but god forbid you need their help with something.