All OnSIP services are billed in advance. You have two separate ongoing balances as an OnSIP customer:

• Plans: Monthly charges for your application services or per-user charges
• PSTN (Prepaid): Pay-as-you-go calling credits and phone number charges (per number) as well as toll-free inbound and international dialing

You can view your Plans/Per-user balance and invoices by navigating to the "Account" tab in the OnSIP Admin Portal, and then heading to the Plans box.

The PSTN (Prepaid) box there refers to your pre-paid calling balance, which must remain above $0.00 to make and receive calls to/from the PSTN.