REFUND REFUSED

I own a franchise company . Daily we do Cash Up showing how much we made for the day. On Saturday 2nd June 2018 I was making ATM deposits for a few days(as it was a slow week) and only R27 210.00 was deposited. The other money was deposited but rejected. The following morning I went to the branch(Mall of the North) to complete the refund application form. I was missing over R24 000.00. FNB only refunded R10940.00 they said they not sure how much I deposited and will only refund that . I have proof of how much was done daily from the Cash Ups/ The franchise Head Office system which shows daily how much was received/ sold. Its so devastating when you trying to make a living for yourself and the Bank refuse to refund the money you work so hard for