It sounds like you have a subscription for Apple TV +, that is not the same as subscribing to all the content in the Apple TV App. Perhaps this will help you understand:
Apple TV+ is $4.99 per month, everything else in the Apple TV app are additional charges. If you are unclear on what the difference is between Apple TV+ and what the Apple TV app is it's pretty simple.
- The Apple TV app is simply a single place to go to buy content, including Apple TV+ content, Showtime, CBS, and lot and lots of other content.
- Apple TV + is Apple's own content, currently it is a small library of content which is why it is inexpensive. The good news is the library is constantly growing and adding some pretty good content!
If you are still confused please visit www.apple.com/tv and look over Apple's TV offerings which include:
- Apple TV HD (hardware)
- Apple TV 4K (hardwares)
- Apple TV app (as described above)
- Apple TV + (as described above)
- AirPlay
- Accessories