No unit upgrade after 36 months and unfair credit agreement continuation

Altech Netstar is now scrupulously deducting monthly tracker premiums on a unit that has exceeded 36 months rental period. The retention department is no longer contacting customers to do upgrades and prefer to continue with monthly premiums on a paid-up unit. During the 36 months rental period, Netstar is charging premium for Hardware, installation cost and tracking cost/airtime. However, after 36 months the hardware and installation cost should be paid-up and premium reducing. However, Netstar is not doing such reduction and continues to debit monthly premiums. I have called the retention department and queried why have i not been called by the Retention department like how it used to be done in previous years. The guy who I spoke had said that my premium could only be reduced by R50, however the June invoice is now reflecting the normal premium. So i have now been blatantly misled by the Retention personnel and can be confirmed through the notes on my accounts. This is unfair credit practices by Netstar to make profit on paid-up rental units by continuing to charge normal prices and not contact customers to upgrade units.