The Gateway PRO, code 215015/215015 BLK, for wireless multi-zone temperature regulation with built-in GSM, UMTS or LTE modem requires the use of a micro SIM. If you are experiencing problems with connecting to your network, we suggest you check the remaining credit on your SIM card and make sure that the PIN code is disabled. Try removing and reinserting the SIM card carefully and then try connecting to the modem again using the CALEFFI CODE^® app. If network coverage is poor, you may want to consider changing your mobile phone service provider.