As you are billed through a third party (Apple iTunes or Google Play) you will need to update your payment details with the third party you have subscribed through.

If you have subscribed via Apple iTunes, you will need to update the payment details associated with your Apple ID. You can do this using the following steps:

1. Go to your Apple device’s Settings and select your Apple ID.
2. Select Payment & Shipping.
3. Select Payment Method, then edit your payment details. Make sure your name and billing address exactly match the information on file with your financial institution.
4. Then select Save.

You can find out more about updating your Apple ID here: https://support.apple.com.

If you have subscribed via Google Play, You will need to update your payment information associated with your Google Play account. Please follow the below steps:

1. On your Android phone or tablet, open the Google Play Store app.
2. Select Menu and then Account.
3. Tap Payment methods and then More payment settings.
4. If prompted, sign in to google.com.
5. In your browser, select Menu and then Payment methods.
6. Under the payment method you want to edit, select Edit.
7. Make your updates and select Update.

You can find out more about updating your Google Play account here: http://support.google.com.