1. Ensure that the module’s SIM_PRESENCE pin has been connected
2. Enable SIM card detection via AT command

Example:

AT+QSIMSTAT=1 // Enable SIM inserted status report

AT+QSIMDET=1,1 or AT+QSIMDET=1,0 // Enable SIM card presence detection

When SIM card is pulled out or plugged in, module will immediately respond:

+CPIN:NOT READY

+QSIMSTAT:1,0  or  +QSIMSTAT:1,1

Call Ready