Disappointed with istore!!!

I went and bought earphones at I store in Gateway uMhlanga Durban for R459 with my bank card, just as I leave the store I put them on my phone and I played music, the left part of it went in and out and stopped playing, luckily I was still at the mall I went back after like 5minutes with my slip, they sent me to a tech- in store and he listened kept on playing around with the wire and it played, I told them to replace it they said that’s not how it works I must go back home and if it does it again to come back and let them know, I plugged them in again and when I was about to leave the it went dead again, they refused to give me new ones or to give my back they said they only refund it to credit cards and if I don’t have one there’s nothing they can do. I stood there and they were making a fool out of me because the tech **** and said it is working I should keep testing them. When I told the store manager I will report them he then gave R350 cash out of R459 that I paid they said they are charging me for asking for a refund is that correct?