How can I verify my phone number without sending SMS?

Question

SMS

Hello.
Let's say I plan to launch a service / program in which the phone number is the key link. But I can't use SMS services for financial reasons, stupidly expensive.
Are there any solutions that exist, with which you can 100% check the ownership of the entered phone number. That this is his phone, and not randomly dialed.
As an option, this is something like a public service, a savings bank. But I have no idea if they give a phone number by api. But this is an example of how.

I am looking for a global solution, not only in Russia.

Answer 1

You can try some messenger linked to the phone, for example, Viber.
Do all this as follows ... If there is a Viber tied to the phone, then we send the code there, and if not, then we send it by SMS. The so-called chain pattern.
This can greatly reduce the cost of your confirmation check. However, this does not exclude the complete exclusion of regular SMS, since not everyone may have Viber. It can also be a little confusing for the client.
It is worth considering whether it is so expensive. After all, confirmation of the client's phone number is only one time.

Answer 2

Verification via calls is much cheaper than SMS.

Answer 3

Use the FlashCall service. For example , we have .
Messengers have difficulties with covering all users + more complex integration.
To confirm numbers, it is better to use either SMS or flashcall (in cascade with SMS), but flashcall is much cheaper than SMS.