You can cancel the recurring payment for your Plan on Windows from Services & subscriptions.

Please do the following:

1. Go to Services & subscriptions. You might be asked to sign in.
2. Find iStudiez Pro subscription and select Payment & billing > Cancel. If you don't see your subscription, make sure you are signed in to the correct Microsoft account for that subscription.
3. Follow the on-screen instructions to proceed with cancellation. Check your inbox for a confirmation email.
4. You can also find the subscription and select Payment & billing > Change > Turn off recurring billing to avoid being charged again when the subscription expires on its own.

Please follow this link to read more:

https://support.microsoft.com/help/4027815/microsoft-account-cancel-a-microsoft-subscription