Fail to assisgn the right contract USD ***

My name is Tumelo Modise contract number ***, the beggining of June 2015 I went to MTN maponya to do an upgrade as I was due for one. The phone I was interested in was the IPHONE 6 that was on the R459 00 special, but unfortunately they didnt have that in stock and I opted for the IPHONE 6plus. While the consultant was changing my details on the system he mistakenly chose the wrong package which was not for the phone I wanted, whats frustating is that everytime when I upgrade this same mistake happens... and the ripple effect it has its irritating because I will end up being debited wrong amount. My contract (24 months) ended in April 2015. The consultant made contact with the call center to resolve the issue but its been 4 weeks now and I am still stuck with the wrong package.USD *** the only thing I humbly request for is for everything to be cancelled I will go seek another service provider will give me value for my money.