A-party number manipulation that lets a call ride a cheaper route. The B-number says international; the A-number says local. The rate card pays local. We detect the refile before the rate card does.
Refiling, also called A-party refiling or CLI refiling, is the practice of changing the calling party number (A-number) so the call appears to originate from a cheaper trunk. International call becomes domestic on paper. International rate becomes domestic rate on the bill. The settlement gap is the fraud.
We compare the A-number that arrives at each hop against the A-number that left the previous hop. Refiling shows up as a mismatch in the chain.
A-numbers are checked against national numbering plans. An A-number from country X terminating on a Y dial plan is the refiling signature.
Sudden shifts in A-number distribution on a corridor, usually towards domestic ranges on what should be international traffic, flag a refile operation warming up.
The detection principle is simple: track the A-number end-to-end through the call chain. Where it changes, refiling has happened. Implementation is harder, you need visibility at every hop, not just at your own switch.
We capture the A-number as it leaves the origin switch. This is the reference against which all downstream hops are compared.
At every interconnect point we have visibility into, we verify the A-number against the origin-side reference. A mismatch is logged with the hop, the timestamp and the route.
We cross-check the A-number against the destination numbering plan. International numbers dressed as local are the most common refiling pattern.
We baseline A-number distribution per corridor. Drift towards domestic ranges on what should be international traffic flags a refile operation.
If you bill per minute based on the A-number presented, refiling is printing money. The only defences are: (1) end-to-end A-number integrity verification, or (2) accept that some percentage of your billed minutes are mispriced. We do (1).
Worked example
International call to country Y. Direct route rate: $0.18/min. Local termination rate: $0.022/min.
Fraudster refiling the A-number from Y ranges bills the call at $0.022/min on the rate card, terminates it locally, pockets $0.158/min.
10 million refilled minutes per month on a corridor = $1.58M/month settlement revenue lost. That is the math refiling is built around.
Field note
Refiling is one of the oldest interconnect fraud schemes, and still one of the most lucrative. The reason it persists: end-to-end A-number verification requires cooperation across multiple carriers. We bring that visibility to the corridors we operate.
Where we cannot see every hop, we work with partner carriers under NDA to close the gap.
Send us a sample of your call records. We will run the integrity check and report the gaps we find.
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