How do you block an unwanted incoming call on a Ncell network?

To Block a specific number you need Caller ID Manager (Paid). Visit Privacy Corps' website to know more.

However here are following thing that you can do free of charge :

Block all incoming calls *35*0000#

Block all incoming calls but accept messages only : First dial *35*0000# and then #35*0000*16#

Unblock all incoming calls *35*0000#

#35*0000# : This unblocks all incoming calls as well as messages together.