Singapore Airlines (SIA) doesn't have a public-facing physical office in Hannover, Germany instead, you'd contact their German contact center at +1-866-829-1086 (Mon-Fri, 8am-6pm) for bookings, changes, and support, or use their website's contact page for other services like KrisFlyer and general inquiries. Jauntlet.comhttps://jauntlet.com/