You cannot be arrested for ordinary civil debt. If he paid by CC or debit card, he should go back to the bank and see if the transactions can be reversed. Then he should make a complaint to the police for extortion. It is a crime in some states to threaten criminal prosecution for a civil debt. Also doing that violates the federal rules of debt collection in any case.
Report them!
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
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, tell them that you know this is a debt scam and that you are making a complaint to the police for extortion. 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.