Most of this debt collector companies never serve anyone.  They rely on threats to get payment.  You can't be charged with defrauding a company by not paying on a loan.  Or by closing a bank account.  They are just trying to scare you into paying them something.  Don't fall for it.

Just because a voice on the telephone claims you owe a debt does not mean you owe it
If a voice on the telephone claims you owe a debt:

1.    Demand the person give you his or her name, company name, and address
2.     Demand a debt validation letter by US mail.  E-mail no good.
3.    Do not pay  the collection agent or anyone else a  DIME  until the debt is validated.

Of course they won’t do this, no scammer ever will, so simply block their calls and ignore them.

If they are bothering you,

Report them:

http://www.consumer.ftc.gov/articles/0149-debt-collection

Also contact your local attorney general

If they continue to bother you, and you know you do not owe any money,  tell them that you know this is  a debt scam and that you are making a complaint to the police for extortion.  You might have to yell at the scammer and talk over him or her.  Once you get a copy of the police report and they call you again , just read out the  file number and the name of the PD or Sheriff’s office involved.   Tell them you’ll be glad to send a copy to them at whatever address the jack***es are working out of now.