Open Settings → Delete Account. This removes your WhoIsThis account data. It does not cancel a subscription billed by Google Play — cancel that in Google Play first (see How to cancel — Android (Google Play)), or you'll keep being charged.
Open Settings → Delete Account. This removes your WhoIsThis account data. It does not cancel a subscription billed by Google Play — cancel that in Google Play first (see How to cancel — Android (Google Play)), or you'll keep being charged.