Hello @Illia Kliuha,
welcome to this moderated Azure community forum.
Microsoft verifies your telephone number so they know you are not a robot :-)
It could be the number needs an international notation (like +31 for The Netherlands).
If this is not working check for support from Microsoft.
If the response helped, do "Accept Answer". If it doesn't work, please let us know the progress. All community members with similar issues will benefit by doing so. Your contribution is highly appreciated.