CNAM (Caller Name) 101


Continuing the discussion from Change name that shows when I call other users:

Rather than cluttering the OP’s original thread, I’m replying as a linked thread here. The OP asked a specific question and received the correct answer as far as what Republic is able to do. Follow-up discussion, in my opinion, belongs in its own thread.

The first thing one needs to accept is what is displayed on the receiving party’s phone is determined by their carrier and/or their device. The only thing transmitted with a phone call in the U.S. is Caller ID (telephone number) This isn’t unique to Republic, it’s the way the PSTN (public switched telephone network) is designed to work.

If something other than Caller ID is displayed on the receiving party’s end it’s coming from their carrier or their device. For example, if one is in the receiving party’s contacts, typically that information is displayed. And, it’s not just smartphones or mobile phones generally that are capable of storing contacts. The cordless phones I use with my “landline” are capable of storing contacts also.

Otherwise if the receiving carrier is doing something called a dip, CNAM is typically displayed. Dips are not free, so not all carriers provide the service. Republic (and most mobile carriers) do not. I’m aware some other mobile carriers will do so usually as an optional add-on. Most true landlines and fixed VoiP (Voice over Internet Protocol) services do. Nomadic VoIP is a mixed bag. Google Voice is an example of a nomadic VoIP service that doesn’t provide CNAM. If one has a “landline” provided by their cable company, that would be an example of fixed VoIP and probably does provide CNAM.

CNAM information from a dip is derived from matching a database. In other words, the receiving carrier takes the Caller ID, looks that number up in a database, matches the transmitted Caller ID to the CNAM per the database and, finally, displays that to the receiving party’s device. The huge challenge here is there is no central database used by all carriers providing CNAM. There are multiple vendors whose databases are of varying quality. Here are a couple of examples using my Republic number:


This first example (from a facility provided by a VoIP service I do business with) shows the CNAM for my Republic number as being Miami, FL. If their carrier uses this database, that’s what the party called will see.


The second example is from Twilio’s carrier lookup tool publicly available here: Because it uses a different database, it shows CNAM for my number as Saveology (a now defunct local business that “owned” the number before me). If the receiving carrier uses this database, that’s what their customers will see.

Neither Republic or other carriers have any direct control over what gets displayed at the other end. It’s entirely dependent on where the receiving carrier gets its information. As the examples I shared show, the quality of that information will vary depending on the database used for the dip. What Republic can do is broadcast what its customers would like to see for their numbers in these databases. That’s the process described here: How to Fix Displayed Caller ID – Republic Help. The good frequently updated databases will pick this information up quickly. The less good ones may never pick it up.

Bottom line, when one adds in the relative ease of Caller ID spoofing, CNAM is increasingly useless as a means of identifying oneself to those they call. If you’re calling someone frequently, it would be far better for them to add you as a contact.


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Seems like this could be another famous Roland Hint & Tip. Thank you for the info.



One thing we get a lot of tickets about is; 'Why is just my City and State showing as called ID?"

This is usually what the receiving carrier shows if the database entry is blank or the line does not have the called ID name feature on it. The receiving carrier looks up the associated location for the number. This may not always be helpful since the local calling area pool of numbers can be broader that a single town. You may have a number is a nearby local town even if you do not live there. It is not where you live, but where the number lives.




I have several lines/numbers with RW. One was ported in years ago and the others are RW issued numbers. All the phones display the ID name as city/state of the exchange along with the number. It appears the city/state is like a default ID name that comes along with the numbers from bandwidth and RW keeps it unless changes are requested by members?

The How to Fix document says we can change the Displayed Caller ID using one of four formats based upon the account holder or user name… How to Fix Displayed Caller ID – Republic Help After requesting a name change to a first and last name should the city/state be replaced by the requested new name once the databases are updated? Would this change the display name on all lines/numbers on the account that hadn’t been assigned to another user? Understand what call recipients see can vary as @rolandh explained.

Are ID name formats cast in stone by RW or regulations? If account holder George Jones would like change ID name to Bubba or B. Jones can RW do that? Or does George need to change his account name or assign his number to another user? Thanks.




Sean was pretty clear above, “This is usually what the receiving carrier shows if the database entry is blank or the line does not have the called ID name feature on it.”

If the receiving carrier chooses to look it up in one of these databases. Some providers cache for months and months and it could take a long time.

Republic has specific rules. They are as laid out in the rules in that document.



One thing to also understand is DIPs are done before the call is sent to the user so they are paid for whether the call is answered or not. So it can get very costly and is usually charged for by carriers in a breakage model to recoup costs.

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