Horrible customer service

I have SIM card contract with Vodacom. They deduct every month on the 26th . I decided to pay on the 25th last month. They deducted money again on the 27th . I have been calling to them for a refund . They keep on saying that the money is not reflecting on their system . I sent them my bank statement to prove it. I just want my money back. It’s been 4 weeks now . Just terrible customer service nje.