Is Helium Mobile free?

Excuse me, I was just perusing through the details of the Helium Mobile service and I came across the pricing section. Could you please clarify for me, is the Helium Mobile service completely free of charge, or are there any hidden fees or costs associated with using it? I'm particularly interested in understanding if there are any ongoing subscription costs or if there's a one-time fee that I need to pay upfront. Your clarity on this matter would be greatly appreciated.