Billing and bad service

I have upgraded and the amount that I have to pay is more than the contract that I agreed for. I called the call center and they said it is because my contract has not expired yet and need to pay for the extra device after I have asked the sales person 4time at Vodacom about this and he said I won't be paying anything extra, will only pay the contract amount.

Went to the store and the manager did not really want to assist me, is this the way Vodacom lie to the clients to make a sale.