You can do this through the website of the service itself or through the app store where you made your purchase. You can block all you services at once via My Telenet, but it doesn't let you block individual services or products.
App Store (iOS)
- Open your settings
- Tap your name with Apple ID
- Now tap ‘Payment and shipping’
- Tap ‘Edit’ and then ‘mobile phone’
- Then tap ‘Delete’
Google Play Store (Android)
- Open the Google Play Store app
- Tap the menu at the top left
- Select ‘Payment methods’ and then ‘More payment settings’
- Log in if you are asked to
- Tap below the payment method you want to delete, and then tap ‘Delete’ again
For other partners: go to settings and change your payment settings .