Under the laws of all states a plaintiff is required to prove all claims for liability and damages against a defendant. In your situation, the debt collector is required to serve you with a summons and complaint concerning a lawsuit and prove that you owe on the bill. This is required under this country's due process clause under our Constitution.From what you have written, it seems that the claim against you may be the result of mistaken identity and the bank account frozen might have resulted from a lawsuit against a person who has the same name as you. I suggest that you consult with an attorney that practices debt collection defense work.