There is no plan picker at checkout. The activation invoice covers your first month, and from then on billing follows usage: at month end we count the orders each panel processed and match the total to a slab.
Plan A covers up to 5,000 orders, Plan B up to 15,000, and anything above moves to a custom arrangement. The invoice shows the plan name, the exact order count and the amount — hover the plan anywhere to see its limits.
If a payment is missed, reminders go out before anything else happens, and paying the pending invoice resumes the panel. The full chain — remind, grace, suspend, terminate — is automatic and visible on your billing page.