Upgrade cancellation

On the 9th of March at approx 9:00/9:30am my husband was called by a Mondo agent offering to upgrade one of our numbers. My husband accepted the upgrade and was told by the agent that called that we have 10 days to cancel the upgrade. There should be a voice recording of this call, which will show that this was the information given. We changed our minds and decided to cancel the upgrade, we are within the 10 days. It has taken two days of calling MTN and now Mondo with no joy. The agent this morning told us that we cannot cancel the upgrade, that we need to go into an MTN store and change the upgrade plan. We don't want to do this we want the upgrade reversed to the way the contract was before. We do not want to be tied into another 2 year contract at this stage. I asked to speak to the Manager Chantelle Govinden to be told she is in a meeting. I asked for her work email address and was told they don't give this information out. I can understand not giving out private information, but not to give a business email address????? I would like to speak to the Manager Ms Govinden or another Manager that can assist to get this matter resolved.