Paying for a tablet which I'm not even using

I sent my mom in May to get me an iPad from them, a lady sells assistant then called me advertising the Samsung brand to me. I was reluctant but changed as I wasn't there to really see the difference, so my mom tok the Samsung tablet, only a week later I realise that the Tab had battery problems, I was too busy with studies to take it back, and in two or 3 months time I took it back to Telkom, they told me to take it to Samsung, took it there and waited for about two weeks for it to be fixed. Now its back and used it for about 3 weeks, and when I put in any sim card it says sim not available.Took it to Telkom, they told me to take it back to Samsung. My argument is I bought It from them and every month money is being taken from my account and I am not even using it because its always not working or has a problem. I would like a refund or to get another one. I cannot be paying for a tablet that is always out on repairs. I initially wanted an iPad/iphone brand and sales assistant convinced my mom otherwise. I am totally irritated by the poor service and responses I get from TELKOM Vangate Assistance.I guess the reason why she ws selling me that Tab she knew it was old or had problems