Need my refund

Mtn subcontracted Co called. Selling me a home router... I had recently bought a home router. I asked the difference bcos the person who called was saying the premiums were lower abt R200 lower. I asked the difference of which I was there isn't a difference, I asked more than once and the marketer insisted that there's no difference. I realised that the router had a lower speed than the one I have... Then I had to take it back this was within 7days. I went to Midlands mall to return it plus I called to cancel as I was required.. Then I received statements/invoice where I was charged more. I called and enquired why I was charged more. I was told its money for handling... Ive explained that I was **** to hence I don't deserve to be penalised hence I need my refund. Response was I had to b charged... Mtn inconvenienced me with a call waiting for the slower router and drove to Midlands mall I need my refund