Talk to the people who run the trek
No call centre and no ticket queue. Messages land on the operations desk in Thamel and are answered by the same team that briefs the guides — within one working day by email, usually within the hour on WhatsApp.
Send the desk a message
Tell us the route or vehicle you have in mind, roughly when you want to travel and how many of you there are. The more specific you are, the more useful the first reply is.