How do I make sure I am not charged for an app I accidentally downloaded?

First confirm you have canceled any subscription automatic renewal if there is one (if you simply delete an app this does not cancel subscriptions):

Review the information in this support article by clicking on the link to learn how to cancel a subscription from Apple. ➔ If you want to cancel a subscription from Apple - Apple Support

• "If you signed up for a free or discounted trial subscription and you don't want to renew it, cancel it at least 24 hours before the trial ends."

• An existing subscription will normally continue until the end of its term and may then renew automatically. Stopping automatic renewal is effectively canceling it. "If you don’t see Cancel Subscription, then the subscription is already canceled and won't renew." The "Expires" date means the current subscription will just run until then.

• Read the link to see what to do about subscriptions that do not appear in your list.

• Canceling a subscription does not automatically start a refund. If you want to do that:

If you do end up being charged, see how to request a refund for apps or content that you bought from Apple by clicking here ➔ Request a refund for apps or content that you bought from Apple - Apple Support

"Can’t find the subscription that you want to cancel?", click here ➔ If you want to cancel a subscription from Apple - Apple Support

If you still can't find a subscription, contact Apple Support using the link at the end of the support article.