Charged double for one flight

If I didn't go through my statement with a fine tooth comb I would never have known. So on 12 June I contact mango after trying to book online and getting n error. I speak to consultant give him my ID number he makes booking. Little did I know behind the scenes I'm not sure if their system duplicated payment or the other booking went through and didn't send notification but basically it duplicated flights for same day same time for same passenger so I was charged twice as per my Edgar's statement. This needs to be rectified immediately as surely the consultant I spoke to would have seen any other booking in my name when he brought up my details. I want my flight reimbursed for the R750, cos I'm not going to pay twice and travel once