This is what charge backs are for FYI.
“I’m sorry, but you failed to provide a service. Either give me a full refund or I will start the charge back process with my credit card company and you’ll be forced to explain why your refund policy violates their ToS and any penalties that arise from that process.”
Sealion infestations are problematic. Be sure to call your local exterminator promptly whenever you encounter one.