How do you verify that outbound calls actually ring, and what caller ID the recipient sees?
Call a real number on a real SIM that an independent observer controls, and record on the receiving phone whether the call arrived, how long it took to ring, which caller ID was displayed, any name or Spam/Scam label shown, and the call log entry with its state and duration, backed by a screenshot. Your dialer's own logs cannot show what the recipient's screen displayed. Witnio's Voice / Call Assurance records these fields on physical Android phones and signs each result with Ed25519.
Updated September 25, 2026
Why the calling side cannot see the problem
Verification calls, collections, appointment reminders and support callbacks depend on the recipient picking up. Your telephony platform records that a call was placed and how it ended, but not what happened on the other side: whether the phone rang, whether the number was shown correctly, or whether a warning label made the recipient ignore it.
A low answer rate can mean many things. Without observation on a real handset, a team cannot tell a routing problem from a caller-ID problem, or either of them from a label that marks the number as spam.
What an inbound-call observation should record
The first field is the outcome: observed or not observed. The second is time to ring, from the moment you placed the call to the moment the receiving phone registered it. The third is the caller ID exactly as displayed. A number that arrives reformatted, withheld or replaced tells you something about the route.
Next come any name or label displayed, including Spam or Scam warnings, and the call log entry with its state and duration. A screenshot of the incoming call screen ties these fields together, and a signature protects them from later edits.
What an observation cannot tell you
An observation records what was displayed, not why. If a label appears, the record shows the label, the device and the dialer that displayed it; it does not identify who applied it or on what basis. Audio quality and codec behaviour are a separate question and outside this kind of check.
How Witnio measures it
You call a receiving number assigned to you, from caller numbers you declare in E.164 format. Calls are correlated by caller number, and on a shared receiving number a caller number can belong to only one customer. Voice numbers are placed only on phones that can read their own call log.
Each call becomes a run with observed or not observed, time to ring, caller ID, name or label if any, Spam/Scam label, call log state and duration, a screenshot and an Ed25519 signature that anyone can verify. If no call arrives while the receiving phone is healthy, the run is marked silent; if the phone could not be read, it is inconclusive and does not count against you.
Evidence is kept 90 days on Founder and 120 days on Standard. The receiving handsets are in Latin America. System reliability was measured at 1,300 backtests with 100% autonomy (2026-09-15), under injected faults; that describes the system, not any carrier's call completion.
Frequently asked questions
- Does Witnio place the calls?
- No. You place calls from your own numbers or platform; Witnio observes them on the receiving phone.
- Does Voice / Call Assurance measure audio quality?
- No. It records whether the call arrived and what the screen displayed, not audio or codec quality.
- If a Spam label appears, does Witnio say which carrier applied it?
- No. It records the label and the device and dialer that showed it; the reason behind a label is outside what the phone can prove.