Lewis got my account in arrears

I am so frustrated with Lewis Wellington. A few months ago I went to make a payment and the cashier who helped me made a mistake causing my account to go into arrears. I then told them I don't feel that I need to pay the arrears amount as it was not my fault it was her fault. Since then the arrears amount grew more and more. I have contacted head office and after communicating with them I was assured that the matter is resolved and I was told the exact installment I had to make for my next payment. However every time when I go to the store to make a payment these people try to bully me into paying the outstanding amount. Thay are extremely rude and scold me like I'm a child in front of everyone over this outstanding amount and also because they got angry because I contacted head office. Now I don't want to set foot in the store ever again so I sent my husband. My husband also had a falling out with them over this issue as they told him I am placed on a list because my account is in arrears and they threaten to reposes the items that I purchased. This have been going on for a good couple of months and I'm so disappointed in their behavior towards me knowing that this is not my fault. I was also told that it is my account and I just have to pay it