Hi, I just found this online, if you already know it then note down my errors and notify me.
Nexmo is an SMS gateway used to send messages to users' phones. Specifically, I use it for phone number verification through SMS and its just what I need. nexmo.com is their website. With N3522 approximately, u can send 826 messages to international numbers.
Thats the best I have seen, not because of the price but because of their API which is very easy to use. It covers languages such as Python, Java, C#, Node.js and PHP.
You should give it a try... itzFANE