Hey there and welcome to Apple Support Communities abbyw,
We can certainly understand your concern and see you came to us from the article Watch movies, TV shows, and live content in the Apple TV app.
We would like to ask you a few questions in order to get a better understanding. First, what exact version of iOS are you currently using? We ask as the menus and options can change slightly between versions of iOS, and we want to make sure we provide the most accurate steps. You can locate this by going to Settings > General > About. Second, was the subscription purchased through us in the App Store or directly with MUBI? Third, does this issue happen on any other Apple device when you try to use MUBI? Finally, have you tried restarting the device? Restarting while simple can help resolve most minor issues.
While you gather that information, check out this link on how to manage subscriptions and see everything matches up on your side.
Manage App Store purchases, subscriptions, settings, and restrictions on iPhone - Apple Support
We thank you for your answers, they will help guide us to the next troubleshooting step.
Kindest regards!