If he is a debt collector, he can't threaten to arrest you. If he is a constable and is working as a debt collector, he can't use the authority as a constable to collect a debt and I would file a complaint with the state ethics commission and with the attorney general's office under FDCPA
The complaint has been investigated and resolved to the customer’s satisfaction.
Go here:
http://ujsportal.pacourts.us/DocketSheets/MDJ.aspx
go to the drop down box and use participant name. Put in your county. View all of your court cases.
You had a warrant
Google "list of Pa Constables" and that guy is on there. Looks like you had a warrant