A Deleting a Billing Account would automatically terminate all subscriptions and, as a result, would probably also terminate the Premium Membership.
Below are some links to pages that might be helpful, but please contact the corresponding store for more information.

App Store:
https://support.apple.com/102559

GooglePlay Store:
https://support.google.com/accounts/answer/32046

Also, please note that deleting an Authentication Account other than an Apple Account (ibisAccount, X, Facebook) will not cancel your subscription.

You can read about the difference between the Billing Account and the Authentication Account on the “Synchronizing the artworks on your device with Cloud Storage” tutorial page.