Hi Rebecca, since your subscription were made through the iTunes app store, you can cancel it from the settings of your apple ID, from the settings of your device.

Why not just send them an email instead of typing this request on a non-affiliated website? If the subscription is taken out via iTunes of Google Play, you will need to cancel it within each of these stores, i. E., not through the app as the subscription is through them and not OnlinePianist. If it was taken through the website, you can send them an email and they will honor the cancellation from the date of your email.