Paying for the wrong contract

A telkom sales agent sold a data package to me about 2 months ago. When I phoned telkom (let me just say that I struggle to get through and after multiple calls holding for longer than 25 minutes at time) the customer care agent told me that I only receive 5GB per month. That was not what the sales guy sold to me. He sold 15GB per month and a wifi modem. Can we please resolve this as I feel that a product was sold to me that is not what we agreed on.