I want to cancel my Apple TV movies

Apple TV movies are one time purchases. Once bought they are yours. There's nothing to cancel.

Do you mean perhaps the Apple TV+ subscription service? If so see here: Change your subscription plan - Apple Support

Otherwise, you'll need to explain what you are trying to do exactly.

There is no monthly charge for movies. As I said, its probably for the Apple TV+ subscription. Follow the steps in the link provided previously to cancel the ongoing subscription.

Here is the link again: Change your subscription plan - Apple Support