Without having a way to balance the ATM ACH credits into the account and the Cash Out activity, it is very difficult to feel confident nothing fishy is going on.
You need to get things to a point where you are comfortable with the activity. If this means you ask them to get their cash to fill the ATM exclusively from you then you work that out with the business.
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A successful man is one who can lay a firm foundation with the bricks others have thrown at him.
-David Brinkley