Went on a service call today, Lennox brand heat pump. The outdoor coil was up on blocks, so I could not see inside. Had no idea that it already had a bi flow filter drier installed. The unit was nearly out of refrigerant so I performed a triple evac and installed a liquid line bi flow filter drier. Anyway, my question is, should I refund the customer for the filter drier and admit my mistake or let it go? I am just starting out with my own business and learning as I go and it is tough. What would you do?