ASP.NET developers and users have a very much faith in Twilio
]. If you go to any article or resource for SMS-based applications and notification your will find that they (even I remember that the Microsoft Virtual Academy guy did) use the Twilio.
Twilio is a gateway for sending SMS from your applications to mobile operators across globe, yes at a charge
. You can create a new account and simply get your tokens from them. Then start sending SMS from your application. They would guide you throughout the process in a very simple and easy way. Have a look at their documentations and API
: If there is a free service for such expensive task, do not use
. It might be a spam or malware service tracking you or your clients for making money. They, anyway, do get paid.