At+Cgsn - Request Product Serial Number Id; At+Chup - Hangup Call; At+Ceer - Extended Error Report - Siemens M1 User Manual

Technical reference section

AT+CGSN - Request product serial number ID

This command provides you with the serial number of the GSM module. The serial
number has the GSM format.
AT+CGSN
Option Result
AT+CGSN Displays the serial number. In GSM, each mobile telephone is
assigned a unique number, known as the IMEI (International Mobile
Equipment Identity).
Example:
Enter:
GSM module:

AT+CHUP - Hangup call

This command allows you to terminate all calls.
AT+CHUP
Option Result
AT+CHUP Terminate all calls.
Example:
Enter:
GSM module:

AT+CEER - Extended error report

This command allows you to query the reason why the last call was disconnected. The
information returned can be useful if there were problems with connection setup or if
a connection was interrupted.
Option Result
AT+CEER Displays reason last call was disconnected.
32
AT+CGSN
IMEI: 445199518750
OK
AT+CHUP
OK
AT+CEER