http://www.wynasia.com/gsm_standard_codes.htm
When various network functions are selected via the cellphone's menu using the keypad, the cellphone
automatically generates the corresponding GSM network command string and transmits it to the network.
These commands can however be manually entered via the keypad.
Each command is prefixed with either one or two * or # characters as follows:
** register and active
* activate
## de-reister(and deactivate)
# deactivate
*# check status
Once each command has been entered, if it is a network command
(as opposite to a local handset command) it must be transmitted to the network
by pressing the YES (receiver) key which acts as an enter key - this is
represented here with the @ character.(NOTE: that is the send key, such as dial key)
Always enter numbers in full international format +CountryAreaNumber (e.g. +852
12345678).