Bad Service on sending the Part away.

I went to Goldwagen Bellville where I bought my parts on the 11 September 2020. On 12 September 2020 tried to install the Timing Belt Tensioner and the part didn't want to keep the belt tite. On Monday 14 September 2020 I took the part back and I was told they need to sent the part away to be checked if it was my fault. On the 7 October 2020 I get a call back to say that nothing is wrong with the part and it cant get my money back. I had to go and buy the part at other place which cost my half the price that I paid at Goldwagen. This after 3 weeks when somebody called me back. This is bad customer service. I ask the guy that I want my money back as there nothing wrong with the part so they can sell it again.