If this was a previous purchase be aware that the offer is only valid for 3 months after device activation. If you had claimed the offer, but cancelled then the trial would have also stopped. You can go into your account to verify the current status of the subscription. If you simply saw a billing from Apple it may have been for something else, you can check payment history to verify. Also keep in mind that this is for Apple TV Plus, which consists of their original programming only, other content would be from the iTunes store and have separate payments (for rental pr purchase).