Double Debit. No Return of other transaction

On the 4th of February 2015 i refilled my empty tank with fuel to the cost of R490.03. when making payment via debit card the machine had an error and didn't print my receipt but however debited the money from my account. this prompted a long conversation with the person in charge at the garage at the time and i was assured that the amount had already automatically reversed and would be back in my account within 3 working days. i then made a 2nd payment to them which went through without issue to cover the amount as i had been advised the 1st payment would be back in my account within a few days. 21 days later and i'm still waiting for my money to be returned to me. i have been to the station multiple times and have been told \Its being resolved"and i'm tired of going back and forth"