Type *#61# and press call – Check call redirection status.
Cancel all redirections: ##002#
*43# to activate call waiting, to deactivate #43#.
If your phone doesn’t have incoming call barring and outgoing call barring, you can try this. For outgoing call barring dial *33*barcode*# and pres OK. To deactivate it dial #33#barcode*#.
On any phone on any network type in **43# to enable conference calls. You can make up to 7 calls at once
If you need to block SMS reception (if you are spammed by someone) just press this code: *35*xxxx*16# xxxx is your Call Barring code (default is 0000). To remove this barring type: #35*xxxx#
If you want to hide/show your phone number when calling, put one of these codes below in front of the number that you are going to call. (*#30# / *#31# or *31# / #31# ) Works on some networks.
Typing *0# or *nm# on the beginning of a txt message gives you detailed delivery report on some networks.. But turn off reports in message settings before.
When the sim card-pin blocked type **042*pin2 old*newpin2*newpin2*
Warning:
You can try these codes at your own responsibility ! We are not responsible for any malfunction and we don’t accept any complaints.
Important:
If you know any other tips & tricks & secrets about GSM mobile or any other mobile which is not listed here then you can post in Guestbook and it will be updated soon with your name.
immortaltechnology 
ok i will post it….
Can I block a certain number from calling me. I use Ncell sim. Ofcourse, I can block it by reporting it to the NCELL centre, but it also requires a police statement or something like that. I don’t want that problem. Plus, if I block can I unblock that number??? Please reply….
Yes, you can block the particular person’s (xyz) call. On the cell there is the facility to block the call user. ON your cell setting you will find out Black list or Block Number or Ignore Number…etc. Otherwise you can also divert the call of xyz numbers.