A response to a negative review must be thoughtful and strategic in order to address their concern while maintaining a positive image for the business. I would begin by acknowledging the customers feedback, offer a genuine apology for their negative experience, thank them for taking the time to provide feedback and let them know that you're working on the issue and will followup if the issue can't be resolved immediately. Lastly, I would encourage the customer to contact the customer support email to work towards resolving the issue they have.