For some models the phone do not ask for the unlock code or other conditions. In that case. Follow this procedure:
AEG S200:
Do not insert a sim card
Switch on the phone
Type ###1562#2#CODE#
Confirm with send (Green Key)
Your phone is now unlocked you can use the sim card of your choice now
AEG S180:
Insert invalid sim card
Switch on the phone
Once the phone ask for Unlock Code enter exactly: ###1562#2#CODE#
Your phone is now unlocked you can use the sim card of your choice now
Generate your code here: UNAVAILABLE THIS TIME