The subscriber record is the spine
Everything else hangs off one record per customer: who they are, where they are, what they bought, what they owe, and how they pay. Plans, vouchers, invoices, sessions, and support tickets are all references back to that record. When two departments keep their own copy of a customer, reconciliation becomes a permanent job.
The record should also carry identity on the network side — the address or username they authenticate with — so that a person in support can see, without asking anyone, whether the customer complaining about a slow connection is actually connected.
From plan to session
A billing system earns its keep in the loop between money and access. A subscriber pays, the payment posts, the service extends, and the network device applies it — a suspension on expiry, a reconnection on renewal. Every step leaves a trace that can answer a dispute.
Where that loop is manual, the drift starts: someone forgets to re-enable an account, or a service extends in the billing record but not on the router. The subscriber's real experience is defined by what the router does, so the router is the thing that must be kept in step.
Prepaid, postpaid, and vouchers
Prepaid captures payment before delivery and expires on a computed date. Postpaid invoices a period and carries a balance until paid. Vouchers are prepaid with a code — useful when the seller is a counter, an agent, or a printed leaflet, and dangerous if codes can be guessed or reused.
Mixing models is normal and fine, as long as each one has a single owner of truth for the expiry or due date. The moment two systems can set a subscriber's expiry, they will eventually disagree.
Reconciliation and reporting
Money arrives through channels that move at their own speed — instant on mobile money, slow on bank transfer. Reconciliation is the practice of matching every statement line to a posted payment, and treating anything unmatched as an open item until it resolves.
Reporting is reconciliation's public face: daily revenue, renewals due against renewals done, overdue balances, active subscribers. An operator who can read those four numbers each morning already knows most of what their business is about to do.