One message is the whole of it: the hotel area, the session you want, the hour you want it. Someone is awake to answer, whatever the clock says.
Three things move a booking along: a message, a confirmation, a knock. The first belongs to you, the second takes roughly ten minutes, and the third arrives twenty to thirty minutes after that anywhere in the centre. Nothing in between requires you to leave the room, speak to anyone, or be anywhere near a reception desk.
Write by WhatsApp or Telegram whenever the thought arrives. Ideally you already have the room number in front of you, but if you are still in the air, still in a queue at check-in, or still waiting for a room to be made up, send the message anyway and say so — we will hold the hour and take the number when the key is in your hand. Guests at the Schiphol airport hotels are asked to write a little further ahead, since that journey is arranged rather than dispatched and the travel time is agreed with you before anything is fixed.
About ten minutes later you get a name, the time she will be at your door, and a plain yes to the session you described. If the therapist you asked for is already out on a booking, you will be told that in those words rather than quietly sent someone else and left to work it out at the door.
She crosses the lobby without stopping and comes up. There is no call to the room from downstairs and no message sent from the corridor, because both of those are how a visit announces itself to a floor. If you would rather meet in the lobby and walk up together, say so in your message and that is what will happen instead — some guests much prefer it.
Payment is handled at the beginning and then not mentioned again: cash in any major currency at the day's rate, card, or crypto, whichever is least trouble for you. Plans slip in this city — a dinner overruns, a call from another time zone lands at the wrong moment. Tell us as the evening moves and the booking moves with it.
Tonight
Name the room, the hour and how long you would like her there. The reply comes back in about ten minutes with who is free.