The newest triggers added to campaigns include the act of Freezing and Unfreezing.

Use case: If a customer of yours schedules an un-freeze of their frozen membership, an ideal use of this new 'un-freeze' trigger is to automate giving that customer a heads up that their membership will soon begin charging their card again. No surprises means happy customers.

To set this up:

Click Marketing > Campaigns > create a campaign, then an automation and, for the trigger, choose one of these two options.