When you sign up, you are agreeing to the contract ("I agree to the terms and conditions"). Those terms and conditions legally dictate what you are agreeing to and how you will be charged, and what conditions are necessary to break that contract.
They aren't allowed to charge you whenever they please, without customer control, they have to abide by the contract. Unfortunately, most people don't read the contract, and companies put ridiculous terms in there that people happily agree to.
They aren't allowed to charge you whenever they please, without customer control, they have to abide by the contract. Unfortunately, most people don't read the contract, and companies put ridiculous terms in there that people happily agree to.