Failing to inform me of additional costs

A month ago, my contract came to the point of upgrade and I decided to go for the upgrade. I went into the Vodacom store at The Grove just before closing time. I opted to upgrade to the LG G3 on a Smart S package for R369pm. I confirmed with the consultant that there will be very little difference to my monthly installment, as my previous contract was a very similar amount. At the end I was told to pay an admin fee of R150 which I was already surprised about, as I was not made aware of this admin fee. Over the past few days I have been monitoring my Vodacom app and have noticed that my balance due is R529 per month! I called vodacom today, and it was explained to me that because my contract only terminates in 3 months, I still have to pay the handset fee of my previous contract which is R160pm. I was never made aware of this, and at this point I'm not prepared to pay for the additional amount as it is not my fault that Vodacom sales staff are not trained well enough to inform their customers of additional costs. I was surprised by the R150 admin fee, and now I'm surprised by the extra R160pm and I want this extra R160pm to be waived as I feel like I'm being cheated.