Is there a programmatic way to determine the virtual number or not?

Question

Telephony

I conceived a small project to exchange real estate from owners, but immediately thought about protection from agencies. This is how the question was born.
If there is no way, then another question arises. Is it possible to determine whether call forwarding from the phone is set up other than by calling it? It doesn't matter which number. Just like a fact.

Answer 1

smsc.ru/testhlr as an option, check if off what shows

Answer 2

Indeed, HLR requests will help you.
There is a jamb that they do not correctly determine the region where the subscriber is located (roaming mg / mn), but you don’t need this.