********* upgrade practices

I was a Cell C customer for many years. At the beginning of 2017 I switched to Vodacom. I recently had my first upgrade with Vodacom and when I got my first bill it was nearly double what I should have been paying. I contacted vodacom customer service and the shop I had upgraded at and they informed me that, although I have upgraded, I still have to pay the remaining 3 months for my old headset on top of my new contract. I was very certain that Cell C never did this so I contacted them, as well as MTN and both said that they don't operate like that. I don't understand the point of an upgrade if you still have to pay for your old device for another 3 months! Had I been informed of this practice, I never would have done the upgrade eaely and simply waited for the contract to lapse before upgrading. This is really not a very ethical practice by vodacom, and it is very disappointing as a customer to be blindsided like that. I will not be upgrading next time with vodacom and I'll move back to Cell C.