I have an airtel prepaid phone getting many unwanted calls and SMS. I want them stopped immediately.Please advise me the the method not involving payment. I have tried the good old Start 0 SMS to 1909 which was in use in 2011. It does not work it appears. So please give me the correct method to block these nuisance calls and messages. Regards

AS per airtel you can also call 1909 and activate it through IVR.

Airtel says:


SMS "START <Option>" or "START <Option>, <Option>" to register your preference for receiving selective categories of promotional SMS', to 1909. (click here to know Preference Options)
In case you want to stop all promotions, SMS "START 0" to 1909.
Or you could register via our dedicated IVR at 1909, from your airtel mobile or landline phone

Thanks Savera for giving me the detailed procedure for DNDing my Mobile from unwanted biz callers.