Vodacom taking my money for 6 months!

I moved out of the country in January, the day after I left my phone contract went from a normal contract to a pay as you go contract. Due to leaving on the 29th of January, the PAYG commenced on the 30th - this means there is no way I could have used any money or credit on this account. I have had a varied payment taken from my account every single month since then, which is 6 payments. I have emailed my signatures, a written afidavit and my ID requesting them to stop this, but I have received no response. It's now about R1000 that needs to be refunded to me and I'm losing my patience. I can't believe I've been ignored, and they can take my money for 6 months! Furious!