Cash crusaders Parklands ****

Hello, i bought an iPhone X at Cash crusaders Parklands for R5300. The I phone was not working properly since it starts touching itself after you use it for at least 10 minutes, the front camera sometimes is doesn't work and the call speaker only works at loud speaker. I tried to give them back the phone and get my money back but they said I can't do that, if I want to give it back it should be in a form of me selling it back to them with a less price of R3300, they tested the phone and then said to me that they won't take it because the call speaker is not working and that's how I found out that the call speaker is not working since I have another phone that I use for calls and serious things, so I did not know that about that iPhone because I was planning to use the iPhone for camera and it's applications, even though I told them that I did not know about that and the problems of this phone they said that they can't take it but they can fix it for me. Since I they did not want to take it back I told them to fix it then, they told me the fixing will take 7 to 14 business days and they'll call me to come collect it but the days has passed and now they are telling me that they are unable to fix the phone, when I tell them to refund me back my money they are now grey ticking me of whatsapp and not responding to my text. The reason why I don't go to the shop for face to face communication is that I'm a student and money is a but tough for me and going and coming from that place it cost me R350 to R400. So please I really need help with this situation.