You can manage your subscription in the following ways, based on where you initially purchased.
Web:Manage your subscription any time on the My Subscriptions page.
App Store:Open your device’s Settings app. Tap on your Apple ID at the top of your screen, then Subscriptions.
Google Play:Open the Play Store app on your device. Tap the Menu icon at the top left located in the Search bar, then Subscriptions.
Once you sign up for Yahoo Mail Plus, your original payment method will be automatically charged when it’s time to renew. Unsuccessful payments result in cancellation of the service.
If you no longer want to subscribe to Yahoo Mail Plus, be sure to cancel so you aren’t charged.
Image Credits and Reference: https://www.yahoo.com/plus/mail?ncid=mbr_ympacqlnk00000008