Ask HN: How do you reach “unreachable” clients?

We are a provider of a service that requires manual renewal (payment) every 3, 6 or 12 months.

Sometimes we can't reach our clients due to various reasons, such as an expired domain, no longer working there, vacation, etc. So we usually try to find someone in their company that can renew the service by checking old emails, company website, google, etc. This usually works, but for personal accounts (ie with a gmail address) it doesn't.

We're thinking of flipping the switch to enable automatic payments, but we like how our clients can truly evaluate if they still need the service before renewing. We also anticipate some problems such as a higher chargeback rate.

The question we have is how do you, at your company, reach clients that don't have valid contact info anymore? Do you go through a similar process?