you have to have the correct APN. if your sim is not specific for IOT then try these APNs: broadband, phone, nxtgenphone. if your sim is specific to IOT then try the apn m2m.com.attz. you must also designate the correct earfcn for each band. for band 2, try earfcn 1000 band 5 2549 or 2450 band 4 2100 or 2300 or 2000 or 2175 band 12 5110