Failed to send SMS. Please help!
What steps have you already taken to check the possible causes listed in the commented line?
What were the results?
If you’re stuck, not knowing where to start, here are some AT commands to help with your trouble-shooting:
AT+CGDCONT?
AT+COPS=3,2;+COPS?
AT+CREG?
AT+CGSMS?
AT+CSMP?
AT+CSCA?