Bad Customer services

Please help I took a loan of R1500 from Finchoice in June then before month end of June decided to Settle the loan because I had money,then I requested a settlement offer they told me to pay R1850 of which I paid same day,then in July I needed some money for Emergency then requested a withdrawal of R2260 with the agreement that I will pay R800 and something as monthly installment I agreed only to find that month end of July I have to pay R1444 that I never agreed on,,,it's the total of R800 of July loan plus R600 of June Settled loan,,,,now they keep calling me and I explained everyday I even Emailed my proof of payment several times but they are not helping,,,what can I do because I don't want bad credit record on my name,,,PLEASE HELP I even can't cancel their Funeral Policy that am no longer interested in