Goldeagen Southdale BAD SERVICE

My experience is normally OK. I bought a part for a Golf MK1 on the 10/03/2018 ... And I spoke to the salesman "Antonio" regarding the part I needed, I explained that the part wasn't for me and I would pay for the part and my client came to Goldwagen southdale to meet me for the part. The part wasn't correct so I walked back into the shop and told Antonio that like I said if it was wrong I would come back to him. Which I did. The part was not used or damaged in any way as Antonio seen me with the part the whole time. I was then told I cannot refund the part ??? Invoice no# ********** 4 Code: A4235 - Description: sensor ALT. Lock up00 Price: R495.00 paid cash. The problem here is that I arranged all this with the salesman, because I wasn't sure of the part. And then I was told sorry !!! There's nothing he can do, and I can leave the part there and he will try sell it and then refund me. I agreed not willingly. I have been phoning and phoning Antonio and he has no care. I asked him if he had the same part I left there and he said they didn't have stock !!! I then rep****, that's great then my part must be sold, he then realized that it was me and then said sorry my part is still there ??? I caught him out !! I am a regular customer of Goldeagen Southdale, they know me there and I am getting nothing but stories and NO Help !!!