You Gave Us More Than We Paid For!

I kept my night class 18 minutes after the normal ending time in order to finish discussing the material so that they would be ready for their first exam the following week.  One of the students contacted my Dean to complain...

Suggestions as to how I should have handled this?  I had told them the first night of class that I would not change the test dates so they could plan ahead. Also, I was going out of town early the next morning and did not have time to redo the test.

I told my Dean to reassure the student that I would not charge him/her for the additional teaching received.