Bought a vehicle and now selling it back

I bought a VW polo in July 2021 at we buy cars in Germiston. They said the car has a problem with the power and I was cool with that because they said we can fix it. I could not fix the problem with the power because of financial issues but I did take the car to VW in Melrose for service wich costed me R1000. This month I contacted we buy cars offering them an amount to buy the car back. A guy by the name of Morne Hattingh came to evaluate the car and said he will get back to me after his superiors have offered a price. The following day, I got a whatsapp message telling me that they can't buy a car like that, I informed them that I bought the car from we buy cars in that condition. How can you sell me a car in that condition and when I sell it back to you, you are telling me that the engine needs to be 100% before you buy it? I had to constantly follow up with Morne not answering calls and answers on whatsapp when he feels like.