插电信物联卡进去无法注网，
AT+CPIN?
+CPIN: READY
OK
AT+CSQ
+CSQ: 5,99
OK
AT+QENG=“SERVINGCELL”
+QENG: “servingcell”,“SEARCH”
OK
AT+COPS=?
+COPS: (3,“CHINA MOBILE”,“CMCC”,“46000”,0),(3,“CHN-UNICOM”,“UNICOM”,“46001”,2),(0-4),(0-2)
OK
Quectel
EC20F
Revision: EC20CEHCLGR06A03M1G