All gmail/googlemail (a free email service from google) users can send to sms to any mobitel customers. This service is available on the chat window on the left side of the gmail window. By refering the number in an international format for example +9471abcdefg where 71abcdefg is you mobitel number. Omit the zero and put +94 for sending messages. You can also reply back the sms and the persons receives it as a chat message. This cool service is especially useful for person like me who lives in some what village site namely Ariyalai, Jaffna where the mobitel 3G coverage slow at my home. Though there is a mobitel 3G tower close to Kanagaratnam Madya Maya Vidyalayam (Stanley College) but Ariyalai is relatively big area and I live in a remote site of the area. From gmail you can send upto 50 messages per day and when you reply back it will 5 more sms back to you. But I have not yet noticed the value grows more than 50. May be google guys will change that later on but it is quite unlikely as they also want people to reply back from the mobile operators. Being said that currenly only 2 opeartors in Sri Lanka namely Mobitel and Dialog do have this feature. I don't own any dialog numbers and my dad is also using mobitel, so I am not in position to say how well it works dialog. For mobitel I have tested both on prepaid and post paid connection and it and works fine.