On the session detail page, if it’s at least 24 hours before the lesson, there is a big red button that says “cancel lesson” (or similar in your language). If it’s a package, there is a button on the package detail page that says “terminate package”. In theory, the teacher’s approval is necessary to cancel the lesson or terminate the package. In fact, on those rare occasions where a student asks to do so, I just verify they didn’t hit the button by mistake, and then immediately approve. I can’t imagine why any halfway intelligent teacher would want to force a student to take classes.
If those options are not available or if you have any more questions, you can go to the support site for customer service, or email them at:
Note that customer service is quickest during business hours in Shanghai, and that italki support has lots of people who speak Chinese.