Vodacom
Move contract to prepaid not processed

I have been to Vodacom shops twice to move my out of contract phone to prepaid, but every time I fill in the paperwork and nothing happens - except of course still receiving the normal contract bills and debit orders. Why cannot they process the request? In the shop they say it is no problem, but they don't do it. I want my last six months refunded as this is clearly incompetence and failure to deliver on promises made at the store front.