I want my money back or else i am cancelling

I took out two cellphone contracts from Vodacom which cost me R109per cellphone contract meaning they should debit R218per month. however they debited m account for R412 which is double the amount they we supposed to debit. i spoke to Carle on the Online chat facility after he realised that i was complaining he just ended the chat session without helping me. while wesley also did the same thing when i tried to find out why did they debit my account two. im unhappy and want my money back or just cancel this whole thing, very unprofessional services.