I spent a lot of time looking this stuff up because I needed it for a website I worked on that had to send out text messages - basically you are after an "SMS gateway service".
Unfortunately in the UK the mobile companies don't offer this service. I am sure they did 10 years ago but it seems that they don't now. There are services and websites that you can use but you have to pay to send messages. Have a google for SMS gateway and you will find a few of them I am sure.