Here is what probably happened...
You deposited whatever you deposited, say $120. You know you have $80 cash and $40 checks.
Teller counts and says "Mrs. Jones, You have $80 cash and $40 checks that you want to deposit, is that correct?"
You say "Yes" because it is correct and you both have counted accurately.
Teller miskeys on the cash screen (I was a teller in undergrad) and we have to list HOW MANY of each denomination on the cash screen. For instance, 1 $20, 1 $50, 10 $1. Teller probably miskeyed in the $1 box without noticing.
Teller sends you your receipt and you drive off- both none the wiser because you both ORALLY verified the correct amounts.
Teller's drawer doesn't match with computer records and she identifies the miskey.
I understand this is frustrating for all involved because you both orally verified the correct amount. If the receipt you received is $20 over what you both orally verified, and the cameras show the amount (which the security department has verified- this isn't done by anyone in the branch but a separate department- hence why you can't just go in and view the tape- most are electronic and not on tapes anyway)...
I would give back the $20 or tell them to deduct it from my account... because it isn't yours to begin with. It isn't a case of "oh well- your mistake in miskeying and now I'm $20 richer." The $20 is not rightfully yours to begin with.
I'm not sure why this is such an issue or why you think the bank is trying to pull one over on you.
