It must be a very unprofessional teacher.I have NEVER cancelled a lesson on italki or in any other place (in a real classroom) unless I was sick or something that I could not prevent. Certainly not for a party. You are welcome to study with me.Check out my reviews and ratings. 

Sorry to hear that you have had this problem.I have, however, had students who did not show up or give me any warning at all. I once had a student who said he had  a "family emergency". I had never had any class with him before and did not get any with him after that cancellation. Most of my students are regulars and I trust them and they are lovely people.

Aegis, I think I can explain.  I was on holiday over the summer.  So, I made myself unavailable for that week but available as normal for the following week when I'd be back home. I thought I'd have better access to the Internet but I didn't.  So, some of my students tried to book lessons for when I'd be back home.  Their requests expired because I wasn't near a computer.  Now, I only make myself available a week in advance.  

@Leigh Mumford - what do you mean by "they try to make a booking"? If you remove that time from your schedule, it's impossible to even request a lesson for that time. If you leave that time up there, even though you don't accept the booking, it still does harm to the student as I stated in my last post. Otherwise no teacher would ever have any reason to black out any time on their schedules.

If I'm wrong, I mean if they are trying to schedule by pm or some other way unrelated to italki's booking system, then I'm sorry for misunderstanding.

@Murillo Costa - Those are all valid reasons of course. But I admit if it happened to me twice, or maybe even once if it's our first time, I probably wouldn't hire you again. Unfair perhaps, but my time is valuable.

@Matteo - Apparently it's some sort of national holiday. He claimed he didn't know until one hour before our meeting time that all his friends were going to meet him. Right. And I echo your experiences with Russian, Spanish, French, Thai and Japanese teachers; always on time, or have a valid reason and a reasonable amount of time for cancellation. It's just about 20% of my Chinese teachers that I have problems with.

@Leigh Mumford - Why don't you update your italki schedule to disallow booking lessons when you aren't available? Too much work for you? As a student, it can be frustrating waiting for the booking to expire and getting no response. If you're not available, please take it off your calender. Well, at least you don't do what many teachers do - accept the lesson, and then demand a reschedule. I hate that.

In South Africa we have an energy shortage.  During winter we had continuous scheduled and unscheduled power outages.  That was such a difficult time. However I warned my old and new students of the possibility of a no show teacher beforehand and they all understood.  I made up the lessons missed too. I do have another problem though.  When I am out of town I do not have Internet access in the bush.  Students try to book lessons despite knowing that I will be offline.  I don't respond to the lesson request (obviously) and I lose the lesson. A bit tricky when the students think I'm being unresponsive.