Standard bank not paying back my R1000.

Technical issues with Standard Bank resulted in me losing R1000, Standard Bank insists that the money was withdrawn but they are not providing video footage from the ATM to prove their point. The machine despatched 20 R50 notes instead of 20 R100 notes. Their system recorded R50 notes as R100 notes. This should be easy to prove as the ATM have cameras. Unfortunately Standard Bank is no longer responding to my emails. I will ultimately take this issue to the banking ombudsman if Standard Bank fails to respond here.