please help me

Revert the money right now. Don't spend that money. If you have spent that money already, then you'll need to pay the principal amount. Not anything apart from that. It is a simple scare tactic. They will not do anything to you.

They may only threaten you, but they won't be able to sue you since they're illegal. It's true that you're supposed to pay them the principal amount only. If they're illegal, then you don't have to pay them any interest.

Do what the other posters have said and get that money sent back now. If you've already spent it, you should only pay back the principal. And after you get that money out of your account, if it were me, I'd close the account as soon as possible, otherwise they'll try to make withdrawals. If you have direct deposits coming in and can't close the account right now, at least try to get it on deposit only status until you CAN close it. (putting a stop payment on the account is risky, as so many of these companies use several different names)