Incorrect billing and no feedback on query

I e-mailed [Email Removed] on the 19th of February with a query on both my MTN lines. I have a IPhone 6 on my choice 100 @ R 499 a month and a IPhone 6 plus on my choice 200 @ R 649 per month but since I have upgraded in December 2014, I have been billed incorrectly. First feedback I got from MTN was on the 3rd of March from Nosithembele Nabo asking to verify my details, in return I e-mailed back with my details and was told by the same consultant that she cannot assist due to my details being incorrect. (This is after I asked Sandra from the City View Centre Branch in Durban to change my details including my surname, but this was never done). Since then I have not received feedback from anyone in regards to my query however I did received my March statement. No one looked at my account and no-one attended to my query as this is not the fourth consecutive month that my account is incorrect. Once again I have been charged R 801.00 for a IPhone 6 plus on my choice 200 @ R 649 per month and R 645.35 for a IPhone 6 on my choice 100 @ R 499 a month. I await you feedback