Product: Credit card or prepaid card

I have a Loft Mastercard with Commenity Bank. They had a promotional offer of XXXX fee balance transfer, with 0 % interest until 2020. The only requirement is to do a required payment as per the credit card agreement. As per the agreement that payment should be : " The minimum payment for the Waive Interest, Payment Required and Defer Interest, Payment Required Credit Plans will be the greater of : ( a ) {$5.00} ; or ( b ) 1 % ( rounded up to the nearest {$1.00} ) of the New Balance shown on your Statement for that Credit Plan. '' So, in my XX/XX/XXXXStatement, the balance was : {$930.00}, but that balance includes a promotional balance transfer of {$400.00}. 1 % of this balance is {$4.00}, which rounded up to the nearest {$1.00} is : {$5.00}, so the required payment for the month for the balance transfer was : {$5.00} Subtracting the transfer, the revolving balance was : {$520.00}. And according to the agreement, I needed to pay : $ XXXX+ {$5.00}. I paid : {$530.00} in total. So I paid a bit more than what I needed to pay. 
In my XXXX statement I see an Interest Charge of {$8.00}, which is the interest for a balance of : {$370.00} ( I don't know how they came with that amount since only the amount unpaid was the balance transfer, with 0 % interest ). I also see in that statement that they applied {$10.00} to my balance transfer, which is twice the amount they should have applied. 
I contacted them using their message center and the representative explained that as per my agreement 1 % of payment is required for a balance transfer, he also told me that I needed to pay the revolving balance + 1 % of the transfer. I told him that's what I did, and asked him what happened and why did they charged more, but he couldn't explain why they applied {$10.00} instead of {$5.00} to the transfer. In their last message they told me to call them. 
I called them and the first representative struggled a lot trying to calculate 1 %, she even mentioned that {$10.00} is 1 % of {$400.00}, then she told me that my agreement said I needed to pay 2 %, But I had my agreement in front of me and it doesn't say that. Also, I told her that {$10.00} is not 2 % of {$400.00}. She kept struggling a lot with the calculations, so she decided to transfer the call to her Manager. 
I spoke with the Manager and she was very very rude and condescending. I explained everything and she said that they included in my statement that the minimum payment required for the balance transfer is {$10.00} and I told her is not there ( I had it printed ), but then she changed her mind and said that it is in my agreement. Since I had it printed, I told her that was not true and told her about the 1 %. Then she told me that she could allocate {$5.00} out of the {$10.00} paid to the transfer to my revolving balance. So I told her that if she does that, then they should not charge interest at all and they should credit the {$8.00} back to my account. Because I paid as per the agreement and I have a balance transfer with zero fees and zero interest. She said she can't do that ( they do, because this is not the first mistake they do and in the past they credit back to my account the interest charged ).  So, I'm afraid because they will keep applying whatever amount they want to the transfer instead of the amount included in the agreement and also, they will keep charging me interests. I have written in the email with the customer service rep and my agreement that I need to pay {$5.00} or 1 %, but they won't honor that and will do whatever they please. I'm very concerned, because I have an excellent credit report an excellent payment history and I don't want them to ruin it. So I need your help. 
PS : when you check my agreement, go to page 6. 
Thanks!