We arranged for a transfer from Berlin airport to our hotel. Although the driver had the correct name and address of our hotel, he left us stranded in an unfamiliar part of Berlin at night. Despite our protests, he insisted it was the right address and drove off. When I contacted the coordinator, he said he couldn't help us. We were left with no choice but to walk for 20 minutes in the dark, dragging our suitcases until we located our hotel using Google Maps on my phone. I filed a complaint the very same day, and now, 11 days later, I've yet to receive a response. They had already charged me for the service before my trip.