AT Commands

Here are few of very common AT commands listed down for use:
AT: to check weather AT commands are working proper.

Call Control:
ATA: answer the Call.
ATD: Dial a call

AT+CGDCONT? : To know APN profiles on phone
AT+CGDCONT=<cmd>, <n>
                                cmd : 1/0 (Activate/Deactivate)
                                 n: number of profile index

Basic Information of Mobile:
AT+CGMI: Name of manufacturer
AT+CGMM: Model number
AT+CGSN: To get IMEI
AT+CGMR: To get software version

Basic information of Subscriber:
AT+CNUM: To get MSISDN
AT+CIMI: To get IMSI

Current Status Of phone:
AT+CREG? : Query
AT+CBC: Current battery charging query
AT+COPS? : Query for current operation state( like operator)

Security Related:
AT+CLCK: Facility locks opening or locking
AT+CPWD: To change password
AT+CPIN? : To check SIM Status

if you want ot know more in detail about AT command please leave a comment.