Instalment calculation

<p>Im not happy on how my instalment is calculated, i bought stuff in december which i asked them to put them over 6months period. I couldnt make payment come end of Jan and end of Feb i made a payment of R3000 and to myself i thought ive paid in advance and my balance after that payment was R1006. Im suprised that they require me to make a further payment of R977 come end of March 2017, what happened to the 6months term over the purchase i made in december? It simple tells me that there was no point if being asked if u wanted ur purchase over a certain period. I made an advance payment of R840 and u still require a further payment of R977. Please relook into my account</p>