The person you call sees a number they do not recognise

Caller ID is asserted by whoever originates the call, not discovered by the network. That is the whole design of it, and it is also the reason it can be abused: an assertion is only as good as the rules about who may make it. Displaying a number means telling the telephone network that you are entitled to use that number.

An app that let each user display their own mobile number would be asserting a right to tens of thousands of numbers it has no relationship with. Carriers in the United States and a growing number of other countries now verify those assertions and increasingly label or block calls that cannot be attested, so the practice is becoming technically unworkable as well as dishonest. An app that offers to show your own number without verifying that you hold it is telling you something about how it handles its other obligations.

So Telvio presents a number it genuinely holds, consistently, and publishes who holds it. The cost is the unfamiliar number on the first call. The benefit is that the call is attributable to a real company that can be contacted about it — which is why the caller ID register exists as a page rather than as a paragraph in the terms.

Calling line identity is passed from carrier to carrier, and any carrier along the route may replace it, truncate it or drop it entirely. This is common on international routes and completely outside the control of whoever placed the call.

Depending on the operator that finally delivers your call, the person you ring may see (434) 280-0044, a shortened version of it, a different number belonging to a transit carrier, or no number at all. None of those means anything went wrong at your end, and none is something a setting can change.

The practical consequence is worth planning around: if you are calling somebody who screens rigorously, the number in their address book may not be enough on its own. Arranging the call in a message first is the reliable version, and it costs one line of text.

Some of the people most worth calling are the hardest to reach this way, and it is usually the same people: older relatives, anybody who has been targeted by a scam before, and anybody living somewhere with a serious nuisance-calling problem. All of them have learned not to answer unknown numbers, and that is good advice which happens to work against you here.

The message that works is short and specific: the number, your name, and the fact that it will look American. Something like “when I call you it will show up as (434) 280-0044, an American number — that is the app, not somebody else. Save it under my name.” Naming the strangeness before they see it is what stops it reading as a warning sign.

If they are cautious enough to want to verify rather than take your word for it — which is the correct instinct — send them the page for the number. It is published by the company that holds the number and names who that is, which is a much stronger check than a message from an unfamiliar number claiming to be you.

One thing not to do: do not tell them to call the number back to test it. Nothing answers, and a number that does not answer when called back is exactly the pattern that makes a cautious person more suspicious rather than less.