Some of you don't have customers right now--you have zombies masquerading as customers, but they're no longer real. They're shells of their former selves, and it's not likely they'll ever come back to life. But for the rest of us, since there's no new business to go get out there, the focus has to be squarely on preserving the customers we have by any means that we can support.
That may mean discounts or deferrals or free stuff. It may also mean stepping in and helping them in ways that even 2 weeks ago would not have seemed remotely interesting or necessary. Or it may be just to listen to them--to hear what's on their mind, to help out by helping them process what's happening to their businesses--and lives.
Regardless of the role you're called on to play, ensure they hear from you--not as spam or sales pitches, but as humans first, and a company who cares, second. Going the extra mile is something we should all just be doing right now, if nothing else to ensure our society survives and doesn't collapse into anarchy (and the zombie apocolypse). But beyond that, making sure your customers know you're there for them is some of the best lead gen and sales you can do right now, and it will pay off for you and for your company when this crisis has passed.