car still not repaired after 9 months

I bought a car buy multipotch on finace I drove the car for 1 month and 2 weeks we serviced the car and noticed it had stop smoke in so I took the car for dinostick test and the motor showed it was gone so I spoke to belinda at multi potch she sed that thy will fixe the car after 3 months I go the car back still same condison I send it back after nother 3 months thy told me thy have to replace the engine but belinda by multi potch never called to check how was the car doing I had to call the work shop the wole time I had to do every thing may self no after sales customer service now I told them to cansel the buy and give me muy monne back because it is 9 months later and the car is still not fixed and in between im still making the e payment and is still sitting withou a car so plz I need help what can I do???