i had written code to send data over mqtt using sim800l modem and while developing i have used vodafone 3G sim card and it was working properly but later i moved here in a new state and used different sim (airtel 4G of older state) and it is having a problem now.
please tell me a solution of this problem, if roaming is a problem then is there any AT command to enable roaming or there is any modification needed to make ??
The modules get auto registered even on roaming. Your SIM card must be enabled for roaming, which most of the SIM cards are by default.
Only difference is AT+CREG? will give you +CREG: 0,5 instead of +CREG: 0,1 indicating that it is registered in roaming mode.