Contract cancellation and Refund

I've been with MTN for years. I have a contract with them but their service is poor. Its actually heart breaking.

My first contract was in 2014 then I had an upupgrade in 2016/09/19.. They then contacted me again for a third contract and told me that they will deliver the phones.

Since from 2016 till today I am paying a total of R471 . 55 a month. I have never received my third upgrade but I am paying . I am losing money over a phone I do not have.

I spoke to MTN and I was told I should wright a letter to them explaining the matter and I did. But no cancellation has been made. I also called MTN customer care and a lady explained that I didn't receive the phone cause there is a spelling error on my name and indeed the is but my problem is that MTN never informed me about the phone being returned to the warehouse . So my 2016 contract was meant to end in 2018 but no cancellation has been made. I am really losing money which I have no assurity that MTN is going to return since they are taking money from my account sending me statements whilst they know that the phone they are crediting me was returned to their warehouse

All I really want is a cancellation and the total amount that they have credited me for all these months!!