Using Github student pack I got $50 free credit on Digital Ocean. After 10 months I deleted my droplet. Even though it was billed $5 monthly, at the end I saw that I owe $0.04. I forgot about it for a while, logged in today and saw that I owe $0.15. Minimal transfer from PayPal is $5. How to solve this?
Try contacting their support. Maybe $0.15 is small enough they'll just remove it. Them spending 10 minutes on the issue costs them more than $0.15.
That sounds, to me, like snapshot billing. Any chance you have any snapshots on the account? Toss me an email at jdonnell@digitalocean.com or open a ticket with our support team, we'll take a look :)