I have a credit card through the retail store Best Buy that I made a purchase on with 12 months deferred interest on my purchase. Payment was due XXXX XXXX in full or I would be charged the deferred interest charge. I did not get payed by my job and called to ask to have the due date extended, to avoid the charge and pay it off in full when I got paid. I was assured this would work, but the due date came and I was assessed a late fee. After this I contacted them again and was assured there would be no problems as long as I paid off the full amount within 6 days of the original due date, so I found the funds and paid it off the very day after speaking with them again. Then today I wake up, the deferred interest charges are now on my account, and they tell me that there is no way to remove them even though I was assured they would n't be charged in the first place. I took screenshots of the final chat I had with this company, and am just looking for advice on how to proceed seeing as they are unwilling to work with me anymore after lying to me. 
