Vodacom failure

I upgraded my mobile and data contract in May 2023 via the phone with an agent. Pricing was discussed and agreed upon. A few days later I called Vodacom on an unrelated issue, I found that I was not being billed the promised pricing as per the agent. An investigation about the call was logged, and found that I had a valid complaint. But Vodacom cannot give me the pricing that was promised as it is a fixed pricing on their system. What is the whole point of the valid investigation? Why do we then verbally agree to the pricing over the phone if they are not going to charge you for it? I feel that is *****/ *********.