Vodacom doubles the price without my consent and won't let me cancel

Vodacom sends me an SMS every day telling me I must upgrade my contract or I will be shunted to month to month billing and 'lose access to discounts' (what are those?).

Finally after more than a month of daily harassment I did the online upgrade, when after all was complete they send me an SMS telling me that the price in now more than DOUBLE what I agreed to. I then immediately began trying to cancel this upgrade (and after the experience with Vodacom Customer 'Service' - I am cancelling all services with Vodacom).

I have spoken to more than 15 people, who shunt me from one person to another on a merry go round of incompetence. Nobody can cancel the upgrade. Vodacom seems to have literally no system in place to cancel online orders.

Once this saga is over, bye bye Vodacom, hello MTN.