Google Free SMS to any mobile worldwide:Initially, a credit of 50 messages is given for every gmail account user. You can use this credit to send to a mobile phone across the globe (almost in all countries with supported networks). Every time you send a message, your credit decreases by one. If your SMS credit goes down to zero at any point, it will increase back up to one 24 hours later. So, you won't ever be locked out of the system.
Every time you receive an SMS message in Chat (for example when a phone user replies to one of your messages) your credit increases by five, up to a maximum of 50.
You can also send an SMS to your own phone, and then reply to that message multiple times. Every time you send a reply message, your SMS credit is increased by five. Effectively, you're buying more messages by paying your phone company for these outgoing messages.
For India: Supports All mobile networks
Charges: Free to send from chat to any mobile. If your recipient/friend replies to your sms (to your allotted a number by google for sms), standard sms charges will be applied to the sender as per the tarrif of the operator he is using. No charges for you.
How to stop this service or Problem in sending SMS to DND numbers:
If you no longer wish to receive SMS messages from any Gmail user, you can text 'STOP' to +918082801060. When you text 'STOP' you will receive a message confirmation and you will no longer receive SMS messages from any Gmail user. To reactivate the service text 'START' to the same number.
If your friend is using DND then ask him to text 'START' to +918082801060 to receive your sms.