Product: Credit card

I made a purchase on XXXX for {$5200.00} with a new Wells Fargo account. I had 18 months interest free. If I did n't pay it off by 18 months I would be charged 27.99 %. I made a XXXX purchase on XXXX. If I did n't pay it off by 12 months I would be charged 28.24 %. Before making the second purchase I called multiple times to make sure of all details including interest, payment terms, balance, etc. I called both on and off the record so some of my calls were recorded. I also called the day of my second purchase from the supplier. I 'm not sure if that call was recorded. I was told that if I continued to make the same payments I was currently making the full payment would go towards the oldest purchase. I received a notice on XXXX that I was charged {$1600.00} in interest saying that my first purchase was over the 18 months and was not paid in full. It was then I discovered that they were not applying my full payment to the first purchase. I paid {$290.00} per month for the duration until my last payment ( for the first purchase ) where I paid what I thought was the remaining of {$370.00}. I called in and the first person told me there was nothing she could do. I asked for a manager who told me he only had access to notes and the notes did n't show me asking about payments and all he, or anyone could do was give me a 25 % discount ( {$1200.00} ) if I paid that day. He said he could not send me a copy of the notes and there were no longer any recordings. I got him to send me to his manager who told me he misunderstood and she could look up the recordings but I was not able to listen. She listened to the recordings they did have and said that they did n't contain the part where I asked about how payments would be applied. She told me she did n't have a recording from our call on the day of my second purchase and said if I made a call without entering my account number then that call would not be recorded so it was possible I got the bad information on an unrecorded call. She, however, was able to offer me a 50 % discount if I paid that day even though the previous gentleman told me all anyone could give me was 25 %. I took the deal as I was worried about having to pay the full amount. I also asked how Wells Fargo decided what amount to apply towards the first purchase and the second with each payment. I was told that my statement would not show each payment amount each month and that I needed to figure that out by comparing multiple months worth of statements. Each months statement was clear in showing me the total payment and decreasing total balance but does not show as clearly that those payments were being split up. I assumed, based on what I was told, that the payments were going to the oldest purchase first. If I remember correctly, the last lady I talked to seemed to agree that it was easy to see that I was acting as though I thought payment was being made in full by the due date since my payment was {$290.00} every month until the last payment of {$370.00}. For these reasons, it feels unfair to impose such a harsh penalty. I felt deceived by customer service numerous times and by the unclear layout of my monthly statements.