PLEASE get a lawyer well versed in fair debt collection practices and do all that you can to preserve your evidence

These jerks may have just cleared your debt with that illegal move. It is illegal to acknowledge the existence of a past due debt to a third party. Fines are pretty steep, and people have successfully litigated issues like these

I would strongly encourage you to pursue this immediately and contact several lawyers to consult with over this matter

Hang in there!