Negotiating with valet companies requires a specific approach. They handle damage claims regularly and have established processes. Knowing how to work within (and around) their system gets you better results.
Stay calm and professional. Angry customers get the slow treatment. Present your evidence clearly: pre-park scan, post-park scan, repair estimate. Most valet operators will settle quickly when presented with irrefutable evidence because they know you'd win in court.
If the valet company offers a settlement, get it in writing before accepting payment. Make sure the settlement document says 'full and final settlement' and that no other claims exist. Some valet companies pay one claim but later pursue a different one for the same incident.
If negotiations stall, escalate. Contact the valet company's corporate office, the venue manager (hotel, restaurant, or hospital that contracts the valet), and your credit card company. Some premium credit cards include rental car or valet damage protection as a benefit.