debiting more money

I took out a cell phone contract with vodacom in 2013 around September or October 2013 I don't remember the month quite well everything was going very until I received a call last year around June the guy that called me was offering me to change my package to the u choose package which he advised me that on the uchoose package I will get R350 airtime only and no more data bundle and that I will then start paying R350 only not the R400 that i was initially paying when I took the contract, I agreed to changing the package to uchoose paid the R350 3 months down the line Vodacom started debiting R457.00 from my account ,I left it like that for 2 months thinking that things will get back to normal but 9 months later my account is still being debited R457.00. I called the billing and accounts department for several times and no answers one has answers for me or is able to give me an explanation as to why I'm paying that amount I'm even tired of calling Vodacom. After failing to be assisted after several times I decided that I'm not going to pay the m for end of june because I feel that I've been embezzled what upsets me is the fact that Vodacom was so quick to close my line for no