When a booker opens a cancellation or reschedule link after the policy window has closed, they see a generic system message. We need to customize this text per sub-account (and per language), e.g. "Changes are no longer possible online less than 12h before your appointment. Please contact us at [phone/WhatsApp]", ideally with custom values like {{location.phone}}. Without this, patients get stuck and the policy window creates friction instead of redirecting them to the clinic.