What service can be used to send SMS from one user to another?

Question

SMS

Maybe someone came across:
there is an application in which users rate people from their contact list.
The user wants to be appreciated. From clicks "tell Vasya" and Vasya flies SMS with the text "You were rated in the application name.ru" from the application.
What service can be used to make such a mailing?
For example, sms.ru is not taken.
APD. For example, a similar one (sending SMS through a bot) has already been implemented by the telegram bot @DebtsTrackerRuBot, but I cannot contact the author.

Answer 1

Please explain, "application" is in the sense of an ios & android application? If so, why not send SMS directly from the application?

Answer 2

With the help of any service that allows you to send SMS. Well, naturally, what answer are you waiting for? Go to Google, there are a lot of aggregators that provide api for sending SMS. If you really want to, then understand your smpp-gate and work directly with operators if you can interest them.