Bad customer service

I took a data top up contract 30gb during the day and 30 GB after midnight in November 2018. The consultant made it an open line instead of top up which I discovered upon the debit of my account.

I called Vodacom to inform them and requesting them to rectify the contract to what I signed up for but when the change was made to the top up the consultant didn't effect the original contract of R345 instead I have been charged around R600 which I never agreed to.

I have been calling Vodacom over and over to rectify this matter to no avail and I continue to overpay as I don't want to be disconnected.