Telkom consultants giving us contract we did not ask for and not accounting for their mistakes

I have various contract with Telkom and my data contract was ending and a consultants have called to renew and I had asked to continue with the contract as it was, which required that a pay a fixed fee for certain of data and when finished I will recharge. But the consultants decided to say for some reason when the data have depleted I can still use data up to R 500 before I have to recharge which was not as per the initial contract. Now I have incurred that which I did not even budget for and they send me a invoice expecting to pay R 500 which we did not agree. I can them and they say sorry. You have to pay that amount.

I was a really happy customer but now after my 5 contracts end I guess I will to find another service provider. The consultants must be accountable for the actions not me.

I am not happy at all.