I would call. Even though it is only two dollars. You have a right to dispute every charge. If you have a paper receipt that is even better. Maybe this guy does this to everyone...maybe he doesn't and it is merely an administrative error. It's your money after all.

If there is any charge on my account that I don't recognize/remember, I call in. Doesn't matter how small.

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http://www.thedalzells.org - Where I Live