Money gone and Camera footage on Cellphone?

On Saturday (27/01/2018) at 10:30, I sent my sister to deposit R4,000 to SJ Sthole who is currently building my house. She went to Nedbank (Mandini Branch) at Mandini Plaza. There were no deposit slips and my sister told the cashier that the transaction was for R4000. My sister reached into the bag not knowing that I had given her R4990 and not only the R4000 – she did unfortunately did not check it, but handed the money to the Cashier. We went to Nedbank and I asked for footage, Mr Mthethwa (the Branch Manager) asked me to return on Monday, which I did, only to find out that the footage is in his cell phone - he told me that I’m not allowed to see it in their computer room or to take the footage with me. My big problem is that the cell phone clip that he showed me does not show the amount of the money that was counted by the machine. When I wanted to open the case formally Mr Mthethwa and his assistant did not allow me to do so, they said “they don’t know what to write on the statement”.

I would like this investigated and I would like my R990 to be repaid to me.