If you are getting Unsolicited Commercial Calls (UCC) even after a confirmed registration for Do Not Disturb (DND) at the NDNC/NCPR registry, you may complaint to your service provider. Please note that TRAI or NDNC Registry doesn't take complaints directly and it is your service provider who will handle these complaints.

Send an SMS in this format: COMP TEL NO XXXXXXXXXX; dd/mm/yy;hh:mm; short description to 1909

Here, XXXXXXXXXX is the number against which you are complaining or the sender code in case of bulk SMS without a number. The next two are date and 24-hour time at which you received the unsolicited message or call. At the end, add a short description of the call you received.
e.g. COMP TEL NO 9999900000; 31/01/12; 16:45;ABC Bank about loans