When the phone rings, after you spent 15-30 minutes without touching the site, Peeves (he sounds like wind, honestly) comes and knocks over the cup holding the pens. Or the phone will ring and when you press the button with the picture of a phone, a person says "Hello?" and then hangs up.
The portkey with the question mark or the room with the Do Not Disturb sign that it leads to is meaningless, as far as many are concerned. If you leave the window idle for 10 minutes or so, Peeves will come again (he sounds like the wind!) and the vase of flowers will knock over while he writes on the mirror "Peeves woz ere".
You can see that here >> http://img51.photobucket.com/albums/v157/iconny/peeves.jpg
The phone "riddle" can be solved if you dial 62442 (it spells out magic) and you press the button with the phone on it.