There are many travel agents in Hanoi in the old quarter, mostly with fake Sinh cafe or TripAdvisor signs. Adventure Indochina Travel is the real deal however. We booked with their agent Judy a few months before our trip. She customized a Sapa trip for us just the way we wanted it. We were picked up from hotel and brought to the train station and to the train cabin. Everything in Sapa was arranged and she stayed in touch via WhatsApp to check if we were happy along the way. When the train back was not going due to a landslide she arranged a bus and hotel in Hanoi at the last minute. Would book with them and ask for Judy again!