Are you doing like this?

  1. Access the router UI and record the current IMEI

  2. Get a new IMEI for debug purpose

  3. On the router UI, find “AT Command”, then use the following AT command to wite the new IMEI (for example 861585040740945)

AT+EGMR=1,7,“861585040740945”

  1. Check if you can connect to carrier network. If yes then use the following AT command to save the IMEI to the module.

AT+QPRTPARA=1