Retainer is a Whop app for community owners. When a member's renewal fails, Whop retries for 5 days and then cancels — nobody messages the member. Retainer DMs them from your own support chat the minute the charge fails, follows up twice, stops the second they pay, and counts only the revenue that actually came back. Read-only access, free plan, 30-second install. Free tools: churn calculator, win-back DM templates.