Vodacom upgrade

I assisted my mom with her upgrade on her contract which is a month early. I was then informed by the agent who’s name I cannot remember that we had to pay the handset fee for ONE month as it is an early upgrade, we then accepted this and they sent us an sms stating that the monthly installment would be our rate agreed to plus R410pm. We called to query this and the next agent advised that we would suddenly be paying that extra amount for 3 months even though the upgrade is only a month early. I have asked for the call to be pulled and listened to. We accepted that we will pay that extra amount for the first month only and then suddenly they come with 3 months. This is a knock vodacom has to take as it was agreed to on a recorded line.