Sneaky Vodacom

I am completely confused. I have a contract for 24 months with Vodacom. When i took out the contract, i received a discount for the 24 months. Howeve r the last month of my contract i was invoiced and the discount was excluded meaning i have to pay more. This is unacceptable! I vallec 2 months in advance to give notice of my cancelation and it was not mentioned that i would be charged excluding the discount. When i called into customer care to resolve this matter i was cut off and they haven't called me back. I am highly disappointed by the 'sneaky' behaviour. And i expect this matter to be resolved.