Hello Mickey, all servers and resources are billed on a hourly basis, in advance from a pre-paid balance in your account. Payment reminders via email based on your current usage, will be sent 2 weeks, 3 days and 1 day before your account runs out of funds.
To ensure your privacy, the service will require no proof of identity or any personal information. You may use VPN/TOR and pay with Monero or other privacy coins if you prefer to stay anonymous. And because of that, all payments must be made in advance.
Refunds and withdrawals of unused funds are available under certain conditions, see terms of service for more information: https://www.99stack.com/legal/terms-of-service.