My upgrade was never cancelled.

In Jan i went to the MTN in Pinelands Howard Centre,i upgraded to the Sony Xperia M2.Within a few hours of using the phone it gave me problems.I took the phone back and asked Joslyn at MTN to cancel my upgrade because the phone is giving problems.She said that the contract can't be cancelled because the phone must first be assessed.The outcome came that there was a manufacturing problem.I asked her to cancel the contract and she confirmed it was done.In February I went back to do another upgrade and decided to go for the same phone because I liked the features and for me Sony is the best.Same thing happed the phone gave problems I took it back to MTN and I told Joslyn to cancel the upgrade and contract cause I had enough. So told me that there will be a fee of R2000 that I will have to pay to cancel both my contacts.So I told her that I don't have the money and I will rather just cancel the upgrade and I will wait until end of April to cancel both contracts.I was not aware that she never did what I asked her until my debit order went off on the 20 March.I went back to the store on the same day and spoke to the store manager and told her everything.she would have sorted everything.