Wholesale glossary
The A-number is the calling party number: the origin identity of a call. Under origin-based rating it determines what the call costs, which makes it the target of three distinct frauds: CLI refiling, which rewrites it to a domestic number to dodge international rates; CLI spoofing, which fakes it to impersonate a bank or a neighbour; and CLI masking, which suppresses it so origin cannot be validated at all.
Why it matters
Whoever controls what the call chain believes about the A-number controls the settlement. That single sentence explains most revenue fraud in wholesale voice.
What practitioners watch
Verify A-numbers hop by hop, cross-check them against the destination numbering plan, and cluster them against per-corridor baselines. Domestic A-numbers on international call patterns is the refiling fingerprint.
Related: CLI Refiling Observatory · CLI · OBR