Highly ****ed of client

I upgraded my contract to 1gig per month top up. I was under the impression that I would only pay R299 for the Samsung A50 which is what I was sold and agreed to the terms. To my shock I received a call today (2 weeks later) to discover i have an open line and would be billed. Tried phoning telkom and absolutley no one knows who can assist me. I have been on the phone for the past 2 hours with no luck. I will never recommend anyone to use telkom if this is their attitude towards clients.