Product: Debt collection

In XX/XX/XXXX my husband and I unfortunately were forced into bankruptcy after he had lost his job. All debts to my knowledge were discharged. I had a home business for which I was given a credit card and as I was the sole owner and the card was in my name I was able to add it as well to the bankruptcy. The card was with XXXX XXXX. 
Unfortunately, in many cases if a company has already turned it over to collections they are not always notified by the bankruptcy court as it goes directly to the company. Two years later apparently XXXX XXXX purchased XXXX XXXX  XXXX accounts. My account had apparently not been closed so it was one of those they purchased. I was issued a new number and bill. I explained that this was discharged, but they didn't want to hear it, so eventually they sold it to a collection agency Portfolio Recovery Associates. After several months they sent me a letter trying to collect the debt. I tried to explain the same thing to them, but got nowhere so again I just ignored the bill. At some point it was sent to the credit bureau and that's when I saw it while trying to purchase a new home. The Lender I was dealing with suggested I bite the bullet and just pay them off to clear up my credit, so I paid them hoping as they promised they would remove it from my credit, but they lied and never did. Said they couldn't. When we actually found a new home to purchase we went with another lender who questioned the debt. I told him my story and he said, I shouldn't have let them intimidate me and I was foolish to have paid them. So feeling I had the right to dispute it, I wrote to them and the credit bureau who did an investigation, but that got me nowhere so I just gave up and decided what was done was done no sense in trying anything further. 
However, the next thing I know I get this letter from these people asking for my payment again. When I called to ask why I was being charged, they claim that I was issued a refund by them in XX/XX/XXXX, because it was disputed with the credit bureau, of which I have never heard of any collection agency doing in my life. I told them I didn't get any such check, but the women said I was lying and that I needed to pay it back and she would be glad to take the full payment while on the phone with me. I told her she was crazy and that I hadn't received any so called check and there was no way I was going to pay twice for the same bill. Next thing I know she suddenly says that they did get the check back in XX/XX/XXXX. I found the whole conversation bizarre. Then she asked me if I wanted to apply the check back to the account of which I told her sure, do whatever you want with your check and leave me alone. 
Yesterday XX/XX/XXXX, I got another bill from them with the same thing happening. They claim that they were sending me a new check and I needed to pay them back with it, but if I wanted to I could pay before they sent me the check and this would reimburse me once I got it. I told this woman did she think I was some kind of an XXXX to fall for that load of XXXX, making me pay again without ever seeing this so called bogus check they keep telling me I'm getting. When I asked her like I asked the last lady why would they be sending me my money back when the dispute was considered in their favor and she said it's because I asked for my money back, something I told her that I've never heard of any collection agency doing in my life. I then called the credit bureau " XXXX '' and told them my story, and they too said it sounded like a scam that they've never heard of any collection company refunding a paid debt unless they knew they did it illegally and even then good luck. This company is obviously running some kind of scam to try and collect on the same debt using the check scenario as a ploy. They need to be investigated for fraud.