Not refunding money

My Name is Caroline Mvelase, I was depositing money at Capitec Bank Jabulani mall on the 5th November 2015 at 13:47. I initially had R10,500.00 in my possession and I was meaning to deposit R8000 into my account. I mistakenly gave the teller R10500.00 and said I am depositing R8000.00. the teller then gave me a receipt of R8000 but had taken all the money. When I got home I realized that I had given the teller more than I had intended to deposit and she didn't say anything. I later went back to the bank and informed them about the mistake and was told to come back on Monday because their money is sent out on Friday and they would know then if they have extra cash and call me back. I was told that the bank doesn't have cameras or any other measures to trace the whole process... how because banks are suppose to have cameras. the teller didn't even count the money with me. So I was called back on Wednesday 11th November 2015 and was informed that they couldn't trace the money and because I had signed for R8000 then it means I gave the teller R8000.