"You do not have any subscriptions"

Recently I subscribed to the Shonen Jump app because there was a specific manga I wanted to read, now I am done reading it and would like to cancel the subscription, but when I visit the subscriptions page in settings, it just tells me I have no subscriptions. I know I am subscribed because It is deducting £2.99 from me every month, and on the app itself, it says I am subscribed. On the membership page in the app, there is a redirect to the settings page, but even when I use that, it says that I have no subscriptions. I even tried unsubscribing from the browser version, but it tells me I cannot since I subscribed on an iPhone. I'm not too bothered about the price, but I really don't want to be paying £2.99 a month for a service I don't even use.