Which cell carrier has a particular phone number

I’m trying to figure out which carrier might have a particular number. I realize numbers are now portable so it could have been moved, but perhaps I can figure out which cell carrier originally was assigned a particular number so I can email a text message.

The number is 619-536-8xxx (I assume they’re assigned in at least lots of 1000 so that’s all you need. My first guess is T-mobile, but I’d like to know it I can find out.

If it’s been ported away to another carrier from the original owner of the number your method won’t work. On the other hand, if you send to the general address of each of the major carriers you probably have a fighting chance of it getting through whichever carrier the number’s with now while all the others will fail. Probably won’t help if it’s with a reseller but worth a try.

If you are referring to the 536, that is the central office code. Originally assigned geographically. Within an area code (like your example of 619) all 536 numbers would be grouped within one area, not allotted to different carriers.

Whether this still holds true I don’t know but I have had people remark about my cell phone number that I must be from Lorain OH. I don’t live there but I did purchase the phone and get assigned a number there.

Sure, but I’m puzzled as to the underlying intent here. Why can’t OP just call or text the person to ask what carrier they use?

If they don’t know the person, I doubt they’ll get a reply.

Then there’s the quest of why they’d want to know…

I know the number is assigned to San Diego, and I know that’s where the person lives. I’m also pretty sure that T-mobile is the carrier as that one didn’t bounce, I can’t text because the only cell phone I have is an old flip phone with no texting capability. I can, of course email which is what I was trying to do. I know from past experience that this person will not talk on the phone (nor Zoom) for reasons I won’t go into.

In any case the person has finally been contacted by one of us and the absence explained. Thankfully it is not COVID.

When it comes to mobile carriers in the U.S., originally, they were assigned specific prefixes to use within each area code, and wireless prefixes were strictly assigned to wireless devices (cell phones, pagers, etc.) If you had a cell phone with one carrier, and then switched to a new carrier, you had to get a new phone number, as the prefixes were carrier-specific. As a result, back then, if you were knowledgeable about which carriers had which prefixes, you could figure out which cell phone carrier a particular person had, by their phone number.

This was changed in 2003/2004, when the FCC implemented “wireless local number portability” – since then, you can change carriers, and keep your original number. This is the gist of the OP’s question – he knew the person’s number, but that no longer can effectively act as a shortcut to determining the person’s carrier.

Google “nxx lookup”.

Here’s the answer from my favorite NPANXX lookup:

That NPA NXX was assigned to Cingular. Which now, after various mergers, renames, etc., is AT&T Wireless.

So if the OP’s target phone number has not been moved via number portability since it was issued, the AT&T email address for mobiles (10-digits@txt.att.net) ought to work.


Cellphone carriers fought tooth and nail against people taking their number to a different company. Luckily they lost that fight.

You get an email address for mobiles!

I have always wanted a way to send email to text, but it’s not generally available in Australia. Google tells me (which I did not know before) that it’s because Australia is mostly a “sender pays” system, where you need to pay to send SMS messages.

Yes, but …
You get an email address that serves as a “gateway” to the SMS system for delivery. So the mobile user receives it as a text message. Which means among other things the “subject” field and the rest of the email header info is lost.

And now you have a convo proceeding in two comm channels. The recipient can’t directly text back since there’s no phone number associated with the email when it arrived at the gateway. As mobile devices have gotten more “computery”, it becomes easy enough for the gateway to include the sending email which the recipient sees in their SMS app as a clickable “mailto:…” link that, when tapped, fires their email client to compose a reply.

But back in the early days where SMS was a carrier function and any browser or email was a 3rd party function, not so much. App-to-app integration or even communication was anathema at that time. Or on T9 devices from the pre-“smartphone” era.

So in a sense, the SMS can serve as a call on “the hailing frequency” to begin an email conversation on the “working frequency”. At least nowadays.

There’s another big irritant from the sender’s POV. Which is the topic of this thread. Given the 10 digit phone number there is no directory anyone or any app can consult that reliably maps the phone number to the corresponding email->SMS gateway address.

At one time back around the turn of the century (golly that sounds quaint, almost Edwardian) I was responsible for maintaining a system for mass-blast SMS. Back then there were literally hundreds of mobile service providers in the USA. Each with a distinct gateway domain name. Obviously long-tail applies, and the then Big 5 carriers covered 80+% of the users. But this was public-facing and had to cater for “100%” of users, or so the BizCritters told us.

Due to the still-regional nature of mobile carriers back then, any given state or region would have it’s 2 or 3 “big” small carriers. Which would be completely absent 4 states away who in turn would have their own big smalls.

And darn few Americans even today know this feature exists, so if you ask an end-user to supply the email->SMS gateway address of their mobile phone they simply respond “huh?” Which is what drove us to have to know every mobile carrier in the land so we could ask the 2-part question: 1) What is your mobile number? and 2) Who is your cellular carrier? Most users could get that right. Mostly.

And of course the cellular carriers were constantly going into and out of business, merging, renaming themselves, etc. Which constantly invalidated our table of carriers and the domain name stored for any given carrier.

Once mobile subscriber number portability came in, then end users could move carriers. Which didn’t change their mobile number but did change their gateway domain name. Our market was B2B, B2G, & G2B where you would think you’d have a more disciplined conscientious userbase who’d tell us these things, or at least notice when the flow of email->SMS messages dried up, usually just after they got a new phone. Well, we thought wrong about that too.

But yeah, there is an email address associated with every mobile in the USA. And because of our receiver-pays culture, there’s a disclaimer on every website asking for this info, or simply the mobile number alone:

We might send you an SMS. If we do that, your carrier might charge you money for that. That’s your fault, not ours. It’s your responsibility to pay them without whining. Click [OK] to agree.

Bottom line, it’s the usual USA cock-up where the idea was thought through about 10% of the way, released into the wild, then all the harder, less shiny parts were ignored in the name of greater short term profit at massive longer term hassle and cost.

Ok, I am now thoroughly confused, mostly because I keep seeing people refer to the US as receiver-pays when that hasn’t been my experience at all. I’ve had cellphones for long enough that I remember when internet access on my cell phone cost $5/month - because it was before smartphones so internet usage was mostly for things like checking the weather report and baseball scores.

But with all the plans I’ve had there was one constant ( from 90 minutes of calling a month to unlimited calls, text and data) * - either unlimited texts were included or I paid to both send and receive texts. Has there ever been a point when it was common for US mobile plans to charge for receiving texts but not for sending them?

  • How relatively expensive calls/text/data were changed all the time. For my first plan, I got 90 minutes of calling for about $20/month. Texts cost .02 to send and .05 to receive. When texting gained in popularity, I got more minutes of phone calls for the same $20, but texts cost a quarter to send or receive- or I could add a “texting package” (which counted both sent and received against the limits) . Now calls and texts are unlimited- it’s really the data that I’m paying for.

Sure you can. It goes back via the gateway and works, at least on Sprint and Verizon and AT&T.

When I was on Sprint, however, they had a flaky MTA that would time out after exactly one hour on occasion when replying from the phone. This would get me in big trouble with the wife because “you never replied”. It was sendmail; the bounce messages indicated that much, but were cut off just before they would have been meaningful. I tried a few times to get through to their actual techs to say “You need to at least customize the sendmail message so it’s not cut off”, but was never successful. Then my company forced me to switch to Verizon, which I had resisted (because, well, Verizon) and I immediately found that they had SVLTE, which Sprint had been promising for years, so I’ve been happy(ish) since, and no bounces.

But we use Hangouts now, so it would have been solved anyway.

Wow. I did not know that. It certainly did not back in the day when I had to fight with this crap regularly*.

I’m on T-Mobile and only use this tech for personal use now; often as a way to bridge when overseas where I have local wifi but not local SMS. I’ll run some experiments and see how it works.

Anyhow, thanks for the update.

* And don’t get me started on how hard they made it to directly submit SMS into the carriers’ systems without going through their email gateway.