First you are only 7 days into this and they may need a little more time than this, I am not making excuses for the bank trust me, since I will hammer anyone who messes with my money.
As it was pointed out the ATM are audited and reconciled from time to time, not sure if they do it daily or weekly or how often but it is done. When this is done, if the machine has more cash then was put in by customers or the bank itself than it should show in the audit report. This is what you want to see is the audit report. The best way to handle this is to go to your local branch where you have your account set up. They are more motivated to help than the person on the phone.
Personally there are couple financial organizations I do not do business with Citi and all their derivatives, what was Mellon Bank, Bill me Later, and BofA because all these companies at one time or another have messed with my money. As far as I am concern they have less then ethical business practices when it comes to handling your money.
I too as someone else pointed use Wachovia and now Wells Fargo, I have been with Wachovia for 8 yrs and used Wells off and on for 20 yrs and I had couple of mortgages with them and they are great to deal with. I did a no cost refinance with Wells took a 30 yr to a 15 yr all over the phone. That alone saved me 10K in refinancing costs. I have been very happy with them and had very fee issues and when I did they cleared them up quickly and to my satisfaction and did not have to escalate it.