Faulty iPhone 7

Good Day, Mid September 2019 I got me an iPhone 7 through a contract from MTN Kenilworth and a week or two later I found out that the phone was faulty so I took it back to MTN Kenilworth. End of November I received a call from MTN Kenilworth that the phone is ready for collection, I went in and checked but the phone was still faulty and was booked in again for repairs. It took them 6 weeks (approx.) to get back to me and re-book the same phone back again for the same repairs. On the 9th of January I was told the phone cant be repaired and MTN repair center has sent a refurbished phone as a replacement. But I didn't sign up or pay for a refurbished phone and the phone is still with MTN Kenilworth. So I am not sure, what and why I am still paying for? I would like to cancel the contract and get the refund for the monies collected by MTN SA? I have put this very mildly, I am way more frustrated by the lack of professionalism, co operation and little or no competency of MTN and its Kenilworth Shopping Center Branch.