You made a REALLY REALLY bad decision. We're seeing this a LOT particularly in Russia. If they have put your phone in Lost Mode, which is one of the first things they do, there is no way to overcome this. Further complicating this is there is no longer any official Apple Sales or Support in Russia any longer.
If they have offered to release the phone by you paying a ransom, DON'T DO IT. They'll just take your money, not release the phone, then demand more money.
By the way, Apple Team is NOT here. This is a user to user only forum, which Apple doesn't participate. But we see this on a daily basis, so I wrote this to help people avoid doing this, but since you've already done this, read this --> https://discussions.apple.com/docs/DOC-250012416
You are most assuredly going to need go buy a new cellphone and learn from this mistake you made.