Vodacom are exhausting to deal with

Last year in August I cancelled my 3G card with Vodacom and asked to be moved from my contract to Pay As You go. Six months later I am still being charged for both as they upgraded both contractors when they should have downgraded them.<br> <br> I have repeated asked them to either prove I upgraded these contracts, which they can't or cancel them and refund me the overpayments.<br> <br> They don't know how apparently. I have wasted so much time and effort on this, I'm exhausted.