In one application, I'm using a LTE modem (A7672E from SimCom) for voice and SMS only services. I want to be sure the mobile operator doesn't charge the SIM card for data connection and traffic.
What are the AT commands that must be issued (or avoided) for this?
After power up, the modem has two PDP contexts activated (AT+CGACT?) and the packet domain service is attached (AT+CGATT):
> AT+CGATT?
< +CGATT: 1
< OK
> AT+CGACT?
< +CGACT: 1,1
< +CGACT: 8,1
< OK
Is it sufficient to use only SMS and voice AT commands (ATD, AT+CMGR, AT+CMGD, ...) to avoid data traffic charge?
When exactly the data connection (and charging) start?