Pin billing
PIN Billing is a legacy billing method used for handling payment without a payment gateway. You can create multiple PINS based on a particular plan. These PIN bunches can then be sold to sub-zones and you can track the number of PINs in use.
These PINs are then distributed to the end subscribers on payment to the sub-zone admins and these PINs can be entered by the subscribers on their customer portal to renew their accounts.