Over charge

I called African bank for settlement quote and was given 430035.37 in March 2017over the phone. agent repeated this amount and I then asked for a letter to be mailed to me. I got to the branch opened the settlement letter and the other amount was different and higher I queried this and branch staff could not answer me I paid the higher amount and went back & called the African Bank and agent Grace Chiwaya confirmed that it was indeed 43000 this was escalated to the Manager Adesh Jadoo in March and no response was provided. I called them recently September and am told that I am liable as I paid the money instore. now the reason for paying i was walking around with a huge amount of money and did not want to risk being ******, secondly interest is calculated on a daily basis and did not want to risk accumulating interest another day i am now told because i paid i admitted to the higher amount. this is day light ******* as no one explained why the two amounts were provided i am requesting a refund immediately had i not paid them at the point 6 months later i would still be waiting for feedback and sitting with a higher interest and balance. i spoke to Bonolo in customer service who promised to sent me a letter that states they are rejecting my claim till now i have not received that letter.