You have so many options to do that.
First one is you can use SMS gateway
You can get the details from the mobile service provides. They provide the SMS gateway access to you and then you can simply pass the messages they given format. (This method is seems like expensive.)
Second method is GSM modem (HSDPA modem)
In this method you have to learn AT-Command to do that. Because of that all the receive and send SMS using AT-Commands.
AT Commands Ref-
Connect GSM Modem through C# Ref-
Three Method is buy thread part API and the service.
kamprasadKkdubey, if this helps please login to Mark As Answer. | Alert Moderator