GSM codes :

Call Diverting

Immediate
To Activate: * * 21 * NUMBER # [SEND]
To Cancel: # # 21 # [SEND]
To Check: * # 21 # [SEND]

Time Delay
To Activate: * * 002 * NUMBER * * (Time 5 to 30 Seconds) # [SEND]
To Cancel: # # 002 # [SEND]
To Check: * # 002 # [SEND]

Conditional
To Activate: * * 004 * NUMBER * * (Time 5 to 30 Seconds) # [SEND]
To Cancel: # # 004 # [SEND]
To Check: * # 004 # [SEND]

No Answer
To Activate: * * 61 * NUMBER * * (Time 5 to 30 Seconds) # [SEND]
To Cancel: # # 61 # [SEND]
To Check: * # 61 # [SEND]

Unreachable
To Activate: * * 62 * NUMBER # [SEND]
To Cancel: # # 62 # [SEND]
To Check: * # 62 # [SEND]

Engaged
To Activate: * * 67 * NUMBER # [SEND]
To Cancel: # # 67 # [SEND]
To Check: * # 67 # [SEND]

To Cancel All Call Forwarding
# # 002 # [SEND]