Unfair treatment

I purchased a time share with Sun Vacation Club, in 2021. It was a payment option of 18 months and quoted +- R900 pm only to be charged R1908 pm I tried to rectify this matter on several occasions with no avail. I did call the managers in question and was told I did choose 10 months, the sales person sent an email stating he made a mistake. I paid R1908 for +- 6 months total R15961.50 + R4293 = R20254.50. Now Sun Vacation Club wants to pay me R1174.50 (SVC) this is what they call a fair amount.