What service for sending an SMS activation code (number verification) do you know?

Question

Android

Hello!
Let's say there is a mobile application, when launched, the user enters a phone number, where the SMS activation code comes. What service do you know to send such messages? Preferably with API, ie. designed for just such purposes.

Answer 1

https://www.twilio.com/

Answer 2

sigmasms.ru
есть отправка кодов в смс или коротким звонком, называется Flashcall, что дешевле раз в 5 при тех же результатах