No Creditor can threaten to put you in jail. Federal Law prohibits that. So they must be scammers.
#2. If you know their number, have the phone company block the number, however if the number comes in as private, or blocked there is nothing you can do about it.
I have tried to get the phone company to stop all blocked numbers from coming in to my phone, but they said they cannot do so.
So dont worry about these people. They will refuse to give you contact numbers, because they look for stupid people who fall for their threats.
You wont be able to trace their calls back, because they are scammers.