How to check phone number by sending sms code?

Question

SMS

Hello!
Please tell me what is the best service to use to confirm the phone number?
I looked at some, they are quite expensive. Are there any other services?
I looked only at bytehand, I did not find others.
In general, I need a person to enter a number, for example, during registration, and he received an SMS message with a code. In general, like everywhere else. He enters the code - the number is confirmed, you can continue the registration.
It is desirable that integration through the API is not difficult)
Thank you all!

Answer 1

every proger should know https://www.twilio.com/sms
it's cheaper - look for country-by-country options

Answer 2

You can use SMSAero - for the price it is quite the best option for the Russian Federation.

Answer 3

https://smsc.ru