Is that SIM300D module?
Try using AT+CNMI=0,1,0 to switch off CBM messages.
You can check, if module is registered wit the following command:
If you want to set URC to automatically sends you a message on registration change, use AT+CREG=1
after this, you will be automatically notified when the module registeres
and when it deregisteres
Now you see, that the first parameter is 1. This was set by command AT+CREG=1.
I hope that helps.