You should use modem port, not com3 or com10
I think it was port 11, Now i wanted to do *124# and i type in AT+CUSD=1 TO ACTIVATE USSD AND THEN DID AT+CUSD=1,"*124# but i got an +CME ERROR: retry operation
you need to check with the network operator if this is expected behavior
its suppose to show me my balance… additional question, can i make calls
You can see here