Mweb's underhanded switching of terms of contract

In September, customers received an email from Mweb stating that the 200GB data contract through Cell C would be cancelled. This led to me having to find an alternative service provider.

Two months later in the fine-print of an email from MWeb mixed in with other MWeb spam mails regarding promotions there is one stating that the debit order will continue to go off for R349, and that the product will be switched to 50GB a month. In this mail there is nothing stated about there being an option to not take the deal at all. Nor does it seem that that they require a sign-off from the customer to change the deal at will. It seems to have been communicated subtly, intentionally in order to continue billing customers for a deal that they didn't originally sign-up for. The measly 50GB went unused for the months following with MWeb expecting me now to pay for a change in the deal that I did not explicitly accept.