a user has paid for a VPN account with the ability to connect a public static address to OVPN
And once the user had paid for it, that record is gone. Someone ordered a static IP address. You take a payment, make an accounting entry in your accounts receivable, and mark one of your IP addresses, on one of your servers, as in use for X months. No record exists of which user paid for which IP address. Your only permanent record is that a given IP address and/or virtual server, is paid until such and such date.
When the time comes, someone comes in, says that I wish to pay for this IP address, for another X months. The IP address's record is updated, and the payment gets logged in accounts receivable. Lather, rinse, repeat.
No idea whether this is how that particular VPN provider runs their business, but it's entirely possible that they keep no identifying records of who owns a particular IP address, just that it's paid for until such and such date, and nothing else. That's all they need to do. And they don't log connections to their servers, and have no records who logs onto which IP addresses.
This expert is a clown./p.