In short
When authentication traffic moves from SMS OTP to voice-based mechanisms, it can affect messaging traffic and associated A2P economics. Operators also need visibility into abusive or unauthorised automated calling patterns that use similar techniques, which is why FlashCall detection usually sits alongside Wangiri and robocall analysis.
The revenue path
Verification traffic is concentrated: a relatively small number of global applications generate a large share of an operator's OTP volume. When one of them switches a market to FlashCall, the effect on messaging revenue is immediate and material, and it does not show up as a lost customer in the wholesale records — it shows up as a volume decline with no obvious cause.
Quantifying it requires correlating the messaging decline with a corresponding rise in short unanswered calls from the same platforms, which is why voice and messaging analysis belong together.
Cross-channel correlation
Guardivia's FlashCall and Voice Fraud Solution ingests voice CDRs and, where available, SIP or signaling events, profiles caller, called-number and route behaviour, and correlates the results with SMS OTP observations from the SMS Firewall.
That correlation is what turns "we have a lot of short calls" into "this platform moved this market's verification off SMS on this date, displacing this volume" — a statement a commercial team can act on.
The fraud that travels alongside
The same analytical techniques detect patterns that are genuinely fraudulent. Wangiri campaigns place near-zero-duration calls from rotating international numbers to encourage expensive callbacks. Robocall abuse generates high-fan-out automated calling that degrades subscriber experience and consumes capacity.
Both share FlashCall's statistical signature — short durations, high fan-out, caller-ID rotation — so distinguishing them is a classification problem rather than a detection one, resolved by looking at destination revenue-share status, callback behaviour and whether the calls correlate with app verification events.
What an operator can actually do
The realistic options are commercial before they are technical. Quantified displacement supports a conversation with the application provider about pricing, an adjusted OTP rate card that competes with the alternative, or a bundled verification product.
Where an operator does choose to restrict the traffic, Guardivia detects and classifies; blocking, rate-limiting or redirecting is enforced through a voice-security component or an integrated third-party voice firewall where technically supported. An SMS firewall alone cannot terminate voice calls.