Collection Agency

I had someone call me stating they were from Advanced Credit Recovery, stating I owe a debt to a PDL. I was told this is up for civil review in my county if I don't make a payment by March 13. I told her that I never got any letter from her company and I would not pay until I first got a letter and then I wanted validation of the debt. She told oh no the orignial creditor has to send me that, which she said they should have and I said no they have not. I just want to know that I believe this place is acting illegally by refusing to mail me anything. And she said if I set up payments she would email my only. They only deal in email and fax, Please let me know that this is in fact illegal and yes they do need to send me something in writing.