Settlement payment not allocated

I had a personal loan account with African Bank that went into arrears due to me going through a bad financial patch. However last year, my finances turned around and I was able to settle most of my debt. I received a settlement letter from African bank dated 1 September 2014. I made the payment on the same day and have proof of both. I noticed this year that upon checking my ITC record that African Bank had never updated my record and still shows I owe the full amount. I queried this African Bank Call Centre and received the following response: MS SOLOMON, Ref no ***8,Good day thank you for logging your query with us,account cannot be closed as we have still have outstanding balance and amount received was never saved unto system and confirmed with lawyers your were given settlement amount of R12664.42,therefore you still liable for payments, your query has been resolved. Thank you, African Bank ***. I believe this is unacceptable as the amount differs from the letter I received as well as I cannot be held responsible if the amount was not saved on their system. I cannot afford to pay twice for one debt. I have confirmation of payment and settlement offer