Product: Credit card or prepaid card

In XX/XX/XXXX I was offered at Home Depot a new credit card, I told the gentleman that my old card was still working and he said that if I got a new card I would get a discount of {$25.00} on my purchase, he never mentioned that I was opening a second account which I would never have consented to. 
I was never sent a statement for that account till in XX/XX/XXXX when I was notified that I was behind in my payments. I called XXXX XXXX who handles home depot accounts and explained to them that I was totally unaware of having two accounts. I asked them to put the total on the old card and closed the new account. They said they could n't do that that all they could do was for me to pay it off and then close it, so I did, right then and there with my bank card. 
Two days ago I went to Home depot and made a purchase and found out that both accounts had been closed. I talked to customer service and explained to them what happened and they made a call and said that they would investigate the problem for me to come back Saturday to check about it. 
When I got home I had two bills in the mail from Home Depot. One for each account. One said that on the new card I still owed a balance and I was late with my payment so they doubled the payment. The other statement said that I owed a balance on my old account, which I do, that I was late with my payment and they doubled the payment. I am never late or have never missed a payment. I make my payments through my credit union with the account number of my old account. 
I went back to Home Depot and told them to please get the mess straightened out. They made some more calls and told me that my payments were getting sent to the new account that I had paid off, and closed, and that I had a credit of {$27.00}, and that they were going to reimburse me by sending it back to my bank. I do n't know where they got that amount as I pay payments of {$35.00}. Did they keep the interest on a payment that was n't even needed on a XXXX balance account? Also, They put that payment on an account that it was not sent to. Who authorized that payment to go to an account with a different number that it was sent to. Also, I have credit on that account but I get a bill with a balance on the same account, How is that possible? 
Any how, Home Depot said it was my credit union that was sending it to the wrong account, I went to my credit union they checked and they only have one Home Depot account number and that is the number of my old account that I send my payments to.. 
I went back to Home Depot and they said they could do no more for me. Please, I am getting charged late charges when I am not late have never missed a payment ever, and I 'm getting charged late payments on the new card that has or should have a XXXX balance and is closed. I am scared to death to make another payment, where are my payments going? Getting charged late fees when I should not be getting charged for. What is going on? If I was n't an intelligent person I could be easily scammed by making that payment on the account I paid in full with a XXXX balance. Good thing I am still a competent XXXX year old. I am not making any more payments until this is resolved. I did make that double payment this month, XXXX-2017, of {$58.00}, that included late fees that were wrongfully applied. I made it just so that I do n't get more late fees, but I 'm hoping it does n't get sent to the wrong account again, or some where else.