Misrepresentation of goods sold and lack of responsibility

I bought an Oxygen Concentrator from this company, as advertised by them on their website. When I opened the box at home I noticed that they gave me a different one, which I have seen being sold for almost R3000 cheaper by multiple companies. I contacted them about that immediately and offered to accept the incorrect device if they would be willing to reduce the price to be around what the device is going for or exchange with the correct one I paid for.

Failing to respond to my email that same afternoon, the following day I returned the device with the hope that they would exchange with the correct one. When I got there, the lady, Chantell, who I arranged the purchase with told me that they do not have the one I bought and that she will need to first send the device to their technicians for inspection before processing my refund, and I will have to wait for about seven days. I asked her if she would have made me wait if I had returned it the same day I collected it and she said yes. I reminded her that she is the one who did not give me an answer the previous day, hence I brought it back the next day, and she just did not care.

Even today, they are still advertising the same device on their website, even though, according to her, they do not stock it because it is an older model. Her excuse for giving me the wrong device was that she did not check before she gave it to me. So now I have to wait about a week to get my money back, for an error she made.