Bad customer service

Have contract with vodacom of which arrangement was R230 deduction for 30months and after a few months of the deduction amount they decided to increase the installment to R313 of which it was a child benefit that was a promotion.... I had done the query with them several times and no one is getting back to me and now they tried to deduct R313 without any communication with me so please Vodacom I need answers and my refund