PHOENIX — Sometime in the next five years or so, some Southern Arizona residents are going to find out that their new neighbors have a different area code.
But no current customer will get a new number.
All this is occurring because, mathematically speaking, the number of numbers available will run out in 2030 in the area that covers everything from Casa Grande and Florence through Tucson, west to the Pima County line and then south and east through Nogales, Sierra Vista and Douglas to the state line.
So the North American Numbering Plan Administrator will have to assign a new code.
The "why'' of all this is more complex.
"I think you've just seen technology explode and the ability to communicate with cell phones,'' said Doug Clark. He's the executive director of the Arizona Corporation Commission, which is involved in ensuring there are sufficient phone numbers available in the state.
"A lot of children above the age of 10 have a cell phone,'' Clark said, each with its own unique number. "My family has six cell phones.''
But that, he said, is just part of the problem. And the rest? Robocallers and spam callers.
"They can request a large pot of numbers so they can, for lack of a better word, disguise that they're calling from Apache Junction or Casa Grande or some other location other than this is an 888 number, so it's a spam call,'' Clark said.
In about five year's state officials expect to issue a new area code for Southern Arizona, but the process will differ from previous years.
It isn't just spammers who are doing this.
There are legitimate VoIP services — voice over internet protocol — which provide services for legitimate companies. Some of their business clients, regardless of where they are located, want caller IDs to show local numbers to appeal to local customers.
And often these VoIP carriers will get large blocks of numbers, perhaps 10,000 at a time.
Clark said his staff is working to separate the two.
"They've tried to be very aggressive with these companies that are requesting these large blocks of numbers,'' he said.
"We can't deny them,'' Clark said.
But he said his staff can discourage them.
"Some of it is by asking questions, 'What are you using all these numbers for?' and 'Why do you need 5,000 numbers?' and 'Is this a spam calling operation, is this a robocalling operation?' '' Clark said. "The legitimate folks who aren't trying to scam anyone would say, 'Yeah, I run a legitimate phone solicitation business and I use these phone numbers for that.' ''
And then, he said, there are "nefarious organizations out there that want this as kind of an arm's length between them and the customer,'' individuals and companies who want to scam someone and then just move on.
So, how to separate them?
Clark said it starts with his staff asking those questions.
"Once you start asking those harder questions, some of the folks go, 'Ah, these people are asking questions that I really don't want to answer. I'll go to another state or another area and try to get my numbers there, and that way I won't have to answer some of these questions,' '' he explained.
"It's only us being nosy and a little persistent.''
It's had some effect.
Before that work began, it was estimated that the 520 area would run out of numbers in 2027, Clark said. What this has done is buy the area three more years.
All this is a simple matter of math.
Theoretically, a 10-digit number should allow for 10 million possible individual numbers.
But many of these numbers can't be used.
For example, you won't find a phone number in an area that begins with 555. No phone number begins with 0 or 1. And the phone company saves others for special services.
What that leaves, according to commission staff, are 792 prefixes, or potentially 7,920,000 numbers within any area code. And that's the number that a split is designed to avoid hitting.
This is actually the second split for the 520 area.
The first split from the state's original — and only — 602 area code came in 1995 when everything outside the Phoenix metro area got the new designation. But that lasted only until 2001, when residents and businesses in the northern and western parts of the state were moved again, at least electronically, into the new 928 area.
There is, however, one big difference in how the newest area code will be created in 2030, one that should make the shift less traumatic.
This time, there will be no geographic split.
Instead, everyone who already has a 520 area code will get to keep it. But new customers will find themselves with a different area code — one not yet determined —regardless of where they live.
That means that, unlike prior splits, no group of current residents will need to notify family, friends and customers of a new phone number. But what it does mean is that homes and businesses that may be right next door to each other will have different prefixes for their calls.
The concept is not unique.
Los Angeles originally was all within the 213 area code. Now, residents and businesses in the downtown area and inner suburbs also have numbers beginning with 323 and 738.
The same is true in the Dallas area, where the original 214 area code now coexists with 469, 972 and 945 prefixes.
While 520 is the first part of Arizona getting an overlay, it won't be the last.
Commission staffers figure that the 928 area code — the one in western and northern Arizona — is expected to run out of numbers in late 2037.
The Phoenix metro area is a bit of a different beast.
That 602 area code that was left after 1995 eventually got split into three parts, adding 480 for the Mesa, Tempe and Chandler area and 623 for the West Valley, including Glendale, Peoria and parts of Phoenix.
But since 2023, new phones in the area have been assigned numbers with any of those three codes, regardless of geography. And that has provided a bit of breathing room, with commission staff estimating the area won't need another area code until late 2047.
