Who Moved My Chair?

This is ridiculoous. Two or three times a week, I arrive at my work hole to find:

• My keyboard height adjusted to maximum height
  
• My chair armrests adjusted to minimum height

This has been going on for a few weeks now, ever since a new cleaning crew started. After a week, I put up a sign that said

Por favor, no toque la silla ni el escritorio. Gracias.
Please do not adjust desk or chair. Thank you.

That worked for 2 days.

Next I tried moving my garbage cans out from under my desk thinking they were doing all the adjusting because the chair was "in the way" of emptying the garbage.

That worked for 3 days and this morning, desk at max, chair arms at min.

Personally, I think this is just management's way of getting people to work late. (I should note that managers have their chairs and desks safely locked away in their office.)