MTN contract

Hello Peter. I encountered a problem with MTN they offered me two phone contracts over the phone in 2018 , accepted it then later realised they are not exactly what I wanted I cancelled before delivery but they delivered , my mistake was to accept the phones but didn't open them but took them back to the nearest store . Monthly later I received messages that I should pay for the contract but when I went to the store for clarity I was told there is nothing that proves that I returned the phones in their system. Last year September I decided to pay for these phone because their legal attorneys kept on calling me I.made an arrangement for a debit order of R1500 . 00 in September then the ramaining amount of R1330 in October but they only debited for September when I called they told me my case is no longer with them I should call MTN head office . I did call them but they gave me another amount to pay different from that I was given by their legal representatives. I need your help to sort this out because it is ruining my credit score .