We work with residential clients, both retail, and as a contractor for a home warranty company. In both scenarios we have to add refrigerant to client's unit(s) to make them run, or provide cold air. In this particular case we were contracted through AHS (home warranty company) to fix an ac unit. We replaced a leaking valve core (this cost is covered by their home warranty, meaning we bill them) and we added 4 pounds of refrigerant, $300 worth. This cost she agreed to pay and signed the work order. Then after her AC was working she cancelled the check.