New Mtn early upgrade rules

Upgraded 4 month ago. Took a cheaper package, obviously to save money. My bank account have thus far been debited with an premium that's much higher then the upgrade premium an higher than the amount I've been paying for the past 21 months. I made contact with Mtn via email and they confirmed that the new contract will only kick in on the 1st of September 2021. Which I could not understand, I then made contact with their customer care champions and I was informed that mtn changed rules regarding early upgrades. According to the consultant this was instituted January 2021. I then asked the consultant to transfer my call to a manager. I hanged on for more than 5 minutes after which my call was disconnected. I informed mtn that I was not informed about their new rules wrt early upgrades and that no Mtn representative told me about this when processing my upgrade.