Hi there,
normally the best way to do this is via your telecom provider - in New Zealand we can do this via 2 different companies "telecom" and "vodafone" - if you just want to send texts via an e-mail it's pretty easy, I would contact the company that provides your cell phone connection - they should be able to point you in the right direction. Vodafone NZ users can set most of this up from the Vodafone.co.nz website.
there are some networks that allow free text messages to be sent to their users (not many) via e-mail/other methods.
have a look at ICQ here:
http://www.icq.com/sms/
(can't see India in that list though.)
good luck
Dan
P.S. - this fourm - "dialogue module" is for discussing a module/feature within moodle - general questions like this that don't relate to a specific module should be posted in the "general problems" forum - or possibly the "open social" forum as this isn't really a moodle related question.