Telkom refuses to cancel my month to month subscription

Telkom refuses to cancel my month to month subscription without valid reason. I subscribed to Telkom FlexOn 6 Top Up for the past year. This subscription comes with MINUTES which I would top up at my convenience. I then decided that I need to couple this with a subscription that comes with DATA, I then called the call centre and I was subscribed for the DATA subscription. I then realised after a month upon receiving the invoice that the subscription that comes with MINUTES was cancelled, and it’s then that they explained that when I subscribed for new package, then the other gets terminated which was not explained to me prior to consenting for the DATA subscription. I requested that they cancel the DATA subscription and reactivate the one with MINUTES but they are refusing saying I have to wait for 3 months. They promised to investigate this and revert back but to no avail. I hope your intervention will help a lot in resolving this issue.