One of the most complex conceptual differences that I am called upon to explain is Caller ID vs. Caller ID Name. Caller ID is, as in the title, just a number. Caller ID is rarely wrong – when it is wrong, it is typically easy to fix. Caller ID Name — on the other hand. Whew. It is an easily broken system, and when it breaks, it is not easy to fix.

Terminology and Abbreviations

Caller ID Number is simply CID.

Caller ID Name is CNAM – if you want to sound cool to others in the telephony biz, please pronounce it “SEE-naam” Rhymes with “See Pam”.

A carrier is the company that gives your phone system access to other phone systems. This is the company that provides your “lines”, “trunks”, “service” and if we bend the truth just a little, your “numbers”.

To the Lecture!

CID works simply. The CID is provided by the originating carrier or the originating phone system, and is passed to the receiving carrier, which passes it to the receiving phone or system. If it is incorrect, typically an adjustment on the phone system will fix. But an adjustment by the carrier will almost certainly fix it. However, carrier technicians are people, and as with all phone issues, tests should be scheduled after any change, don’t take the word of anyone about anything – see it for yourself – get proof. But… then you are done.

CNAM is much more complicated. And there aren’t clear and steadfast rules. But here’s what I have learned.

For illustrations sake, CNAM is an extension of CID. While CID is sent from the originating carrier or phone system, to the destination phone or system, CNAM resolution is a bit more complicated. When the CID is sent to the receiving carrier, the receiving carrier will try to match that number to a name they already possess. They have a table for that. They take that CID, and the originating carrier, and if they can find a CNAM that matches those two criteria – they pass that CNAM onto the recipient phone or system.

Best case scenario? No CNAM entry for that number and carrier. If that is the case, the receiving carrier must do a “data dip” with the originating carrier and ask for the correct name. Easy. But there is a catch. The originating carrier charges the receiving carrier for that data. So now the carriers have a great incentive NOT to refresh their CNAM data. Their bottom line. And the data becomes stale.

This can cause problems when these table entries become stale. It may be that the receiving carrier has a match, but it is from years ago, and is now outdated. But it is still a match. But it is wrong. But it still matches. Wrongly. But it costs them nothing to display that wrong name on a phone, does it? And they can still charge their customers for the service.

What do you do when it is wrong?

The common sense idea is that the originating carrier is sending the right CID but wrong CNAM. Might be. It’s an easy check, if you are the originating caller. You call your carrier, and ask them what CNAM they are sending for your number. They tell you. You correct if necessary. You may be able to convince the originating carrier to broadcast the change, some recipients might listen to that broadcast, and update their records. And that, as the originator, is all that can be done. Because that data is stale on the recipient carrier’s side because of those CNAM “data dip” charges that affect the recipient carrier’s bottom line.

But if it is a stale CNAM entry in the destination carrier database, the destination carrier must clear that entry and dip a new one. The destination carrier must be contacted by someone with a current account with that carrier. Then the problem must be articulated, typically to a technician that does not understand the shortcomings of the CID/CNAM solution. Then one must hope that the ticket falls to someone that has both the power and knowledge to enact the change. To delete that one entry. And that takes us back to “best case scenario”. The receiving carrier has a table with no entry, they ask the originating carrier for a CNAM for that entry, they update their entry. All is well. Until it grows stale. Again.

There are definitely permutations of the above that will break CNAM in other interesting ways. But mostly it comes down to this – if you port (move) your numbers from one carrier to another, please ensure that on DAY ONE the new carrier is sending CORRECT CNAM! Because your originating carrier will never get a chance to send the first data tip to ALL the receiving carriers again. And if it’s wrong on day one, think of all the carriers that will need to be convinced to delete and dip again. Yikes.


Written by Rick Brooke
Photo by Clem Onojeghuo on Unsplash