Vodacom holding back my refund

I am struggling to get my refund from Vodacom for a contract they advice me to cancel as there was no coverage of their network in my area. I have been calling, sending emails with no success at all. I Vodacom was so quick to debit my account but now it take years for them to refund me. when I visit the shop I am always told I will be refunded on Monday how many Mondays must pass before I get my refund, why are holding back on my money as you are not providing me any service.