Promo fee

I have upgraded my handset to a Sony Experia M2 at R245 a month and have been charged a promo fee since upgrading in May. I was not informed of this when I signed my contract. I was assured that I was going to have an upgrade fee once off the following month and that was it. Since then, i received an invoice of R373.99 and this month at R269.83. I am not paying what I signed for. I have queried this and it takes so long for anyone to get back to me. Unathi Njozela did reply on the 17th of July to say that I am paying a fee for the handset that will be broken down over the contract period. This was not explained to me when I took out the contract. I asked further questions as to how much this fee is in total and no one has got back to me. Apparently I can't migrate my contract as it is a promotional contract. Again, none of this was explained. Nevia Moima who handled my upgrade assured me that I would be paying the R245 a month and could have my top up package that I asked for. I am extremely frustrated that none of this is being handled properly. I just want the contract package that I signed up for which was in store at R245/month. I cannot be paying different amounts every month.