Double debited

Vodacom double debited my account, 6 days after I paid my account via EFT. This caused 3 of my debit orders to bounce, costing me an extra R 400 in fees. It's taken me 5 days to try and get it sorted out, still nothing done. They insist on Proof Of Payment, even though the payment was done via EFT, so they have clear proof of where the payment came from. They insist the payment was cash. I find this service unacceptable.