Complain

Last month i received a call from an vodacom agent telling me about upgrading my data plan and i told him i already have wifi at home i do not need it then he said something like they will be adding only R50 from my original plan then i agreed to my surprise on the 7th of July i received invoice saying i will have to pay R500 extra to my original plan which is too steep.i have contacted customer care they said they will reverse it but my problem is that they said they will have to debit that amount month end and I won’t be credited that amount so i feel its unfair the agent ******* me to agreeing to this without telling me the specific amount