There is nothing you can do about it. People that are bypassing paywalls generally won’t pay to subscribe.
You can block individual articles if needed in the Visibility Settings box on the post edit screen.
You can also set the meter to 0 but then your articles won’t show up in search or be shareable. Publishers are moving to this leaky/metered system and away from the hard paywall for the benefits of exposure.
One thought: mobile apps are now preferred by 89% of readers for access to publications. If you offered apps to your readers it would increase the value of your publication and make it much more difficult to get around the paywall.
UniPress will get iOS and Android apps built for you and integrates with Leaky Paywall and IssueM.