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Telco: billing modernization behind a stable rating facade

Problem

Legacy rating engines could not support new bundled offers and usage-based add-ons without fragile branching. Marketing needed weekly experiments; finance needed immutable invoices.

Constraints

Millions of subscribers, strict regulatory reporting, and partner settlements that assumed specific rounding behavior. Any invoice correction wave risked call center meltdown.

Approach

We introduced a versioned product catalog and rating facade that normalized requests to internal engines. New rating logic shipped behind cohort flags with automated invoice diffs in shadow mode for months.

Rollout

Cohorts were chosen by account stability, product mix, and support history—not by geography alone. Each cohort had a rollback switch that restored prior rating without reprinting already-delivered invoices.

Risks mitigated

• Silent invoice drift: nightly invoice reconciliation with tolerances by product class
• Partner disputes: shared settlement artifacts and dispute SLAs
• Org thrash: single “offer lifecycle” process bridging marketing and engineering

Outcomes (illustrative)

Time-to-market for new commercial bundles improved materially while dispute volume stayed flat relative to seasonal baselines during migrations.

Lessons

Billing is a sociotechnical system. The hardest part was aligning rounding semantics across teams that had never written them down.