Vodacom charges for devices long after they are paid off.

After being good customers of Vodacom for the past 11 years, Vodacom states that we are able to upgrade our devices on the 1st of January 2018. When you attempt to upgrade, the system shows you are not able to upgrade because you can only upgrade on the 1st of January 2018, even though it is in the middle of June 2018 already. Furthermore, our contract already expired, with our handsets being paid off months ago, but Vodacom continuously charge us for our handsets every month - Why is that? Then, Vodacom suspends our accounts for both incoming and outgoing calls when we refuse to pay for handsets that were paid off already. We cannot even port our numbers, because Vodacom won't allow it.