If you do not wish to receive unwanted SMS messages or telemarketing voice calls on your mobile phone, you can add your number to the DND (Do Not Call / Do Not Disturb) list.
To get started, just send a text message “START 0” to 1909 and most mobile operators say that promotional calls and SMS messages should stop within the next 7 days.
SMS 1909 Complaint

How to Register DND Complaints through SMS

However, if your number is registered on the Do Not Disturb list and you continue to receive “unsolicited” calls or SMS messages, you can register a complaint by sending an SMS to short code 1909 in the following format:
COMP TEL NO XXXXXXXXXX, dd/mm/yy, Time hh:mm
Here XXXXXXXXXX is the telephone number from which the SMS was received while the other fields represent the date and time of the message.
It obviously requires too many keystrokes to report even spam text message to your cellular operator but if you have an Android mobile phone, a new app called SMSpam by Deepak Jharodia can help you do that with a single tap.
The app works much like the one-click “Report Spam” button in Gmail. It offers a list of text messages that you have received in the past few days and you can tap on any of the spam message to directly report it to your mobile operator. Behind the scenes, the app composes a new complaint message in the format recommended by TRAI and forwards it your operator.
Once the complaint is received, your mobile operator will send an acknowledgment and the status of your complaint will be made available within 7 days of the booking date. This is a TRAI order so mobile operators across the country are likely to follow the guidelines.
SMSspam is useful though I wish the developer had opted for a more soothing color scheme. Also, it can only report spam text messages but not those unwanted commercial phone calls.