How to cancel a Apple account?

Well my sister got a new iPhone and… Well she is over spending and I changed the password on the account last month and some how the bill came to 100$ and since I changed the password my dad thinks I have been spending the money and I need to cancel the account so I don't get blamed.

Downloaded stuff that costs money eh? Password is no matter. Bill and purchases will be labeled to that ID. Apple's servers will always prove that.
Shut if off this way.
http://www.apple.com/...id/manage/
Can't fix the past, but this is all you can do in the future.
It is what it is. Best luck.
http://support.apple.com/.../kb/ht1311

Go to the apple website and there's a link there to cancel the account just like what hugo draxx said