Refund outstanding

I bought a renault triber,and they were suppose to refund me my car installment as I had done a trade in of my kia,took the car on the 22nd of august till today am still waiting for the refund,every time I ask,I get promised a response before the end of business day,but we get to the end of the day without any feedback back,Nothing makes me livid as the after say not being handled properly,I won't be buying from renault ever again.