Are you sure you made the subscription through Apple? I have ex. Spotify on my iPhone, but the payment is not paid through Apple, so in my case I have to go to Spotify's website, and unsubscribe from my subscription.
There may also be an error in the Subscription menu, since you write that it is just "blank". If you have a Mac, or PC with iTunes then you can also unsubscribe there, inside your Account.
If none of this is the solution then contact Apple Support and they can help you unsubscribe.
https://support.apple.com