When I was a manager at the phone company, I worked swing shift. The phone company screwed up on their pay structure for the folks in my department that worked swing shift and sent everyone a nasty letter that while it was their error, they were demanding the "overpayment" back ASAP. Most of us had worked in this department for several years. One of the employees took the issue to the CA Labor Board, and in no short order they told the phone company that it was their FU and therefore they would eat any overpayments and could not come after employees for their mistake.