Friday, March 28, 2008

Wrong Number

Is it time to overhaul the user interface of the phone system?

A few months ago we started getting a lot of calls that were wrong numbers. Before that we used to get maybe one a week, but suddenly we were getting 5 or 6 a day. After an initial period of frustration, we eventually started to apply our debugging skills.

Our first guess was that somebody was distributing our phone number on a flyer or something, either as a prank or by accident. But this didn't make sense because every caller was asking for somebody different. “Hello, is Juan there?” “Hi, Elizabeth/Gary/Tanya/Carlos?” Or the ever popular “<pause> Who is this?!!” No, dude, you called me, so you tell first.

Ok, scratch that idea. Hmm, I suppose we could always ask. “Sorry, wrong number, what number are you trying to reach?” At last, some progress. Our phone number is 987-654-3210 (not our real number). The people who were calling us were uniformly dialing 654-321-0xxx. The 654 area code is for an area maybe 20 miles away, so lots of people in our area code were dialing numbers there. Even worse, there are up to 1000 numbers in that area code that match this pattern. No wonder we were getting a lot of calls!

The reason they were getting us was that they were forgetting to dial a 1 first. Without the 1, the phone system was interpreting this as a local call within the 987 area code to 654-3210, with the extra three digits on the end simply being ignored. On many (most?) cell phones the 1 is not necessary, so people lose the habit of dialing it. Then when they use a land line, where the 1 is required, they get us.

With this insight, we contacted the phone company. It took three tries and many patient explanations to even get somebody to understand what the problem was. I asked what had changed in the system recently, because clearly something had changed to cause the sudden increase in wrong numbers.

“Uh, I don't know. I'll ask our tech guy.” A few minutes later. “Our tech guy says the 321 exchange in the 654 area code is a Cingular exchange. You should call them.” “But how is that supposed to help? The phone calls are originating in your system and never getting out of your system, so even if they made a change over there, it wouldn't change what's happening here.” “Well, you should call Cingular.”

Predictably, Cingular couldn't help. They couldn't even tell us if the 321 exchange was new because “our computers don't tell us that”.

The really frustrating thing about the problem is that it's so easy to fix. It should be easy for the system to detect when somebody has dialed a 10 digits but is being connected to a 7-digit number. Give the caller a warning and ask them to redial! It's possible this might break some systems with extensions, where the leftover 3 digits indicate the extension. So perhaps disable the warning if there is a pause between the 7th and 8th digits.

Has anyone else had this problem?


Unknown said...

This happens to us too, albeit infrequently. Whenever I get a wrong number I ask, "What number are you trying to reach?", and then I usually end up explaining that they might need to dial 1 first.

Kenneth Finnegan said...

Here too. My cell phone gets all the calls to Wells Fargo in the 702 area code. I already know it's a wrong number because they're all random numbers I don't know, so I've almost gone to just messing with these people.

The WORST part is that theres a fax machine in my 1000 numbers as well, so I'll get a fax machine call me, then when it fails, (since I don't speak fluent fax) some fax machines are smart enough to retry, many times 5-10 times.

Barry Kelly said...

Looks like a US-only problem. Outside of US, area codes usually start with a '0', and they're not optional - never optional - on a mobile phone. Mobile phones have their own "area code", and are never "local" numbers like US cellphones.

That doesn't give you a solution... The thing about dialing 10 digits versus 7, I don't think that flies with touch-tone phones. They expect to navigate a state machine where the edges are labelled with numbers. The phone system doesn't get all the digits before it makes a decision where to route it.

Brian Sniffen said...

This change is happening, a bit at a time. Many areas now use "ten digit dialing," in which the area code is always required and the 1 isn't. Then seven digits always gets you a pause as it waits for 3 more... and you realize you've goofed, hang up, and try again.

It's driven primarily by so-called overlay area codes. Old area codes were of the format [1-9][01][0-9]. New York, for example, was 212, the fastest to dial. All the big cities had 1 as the middle digit for speed. New switches are computerized; they don't rely on the electromechanical trick that used the ten clicks of the 0 to switch banks. These new switches can use any three digits as an area code---though starting with 0 still doesn't work so well.

As 212, 617, 718, etc. are filled, new area codes that do not match the old pattern are used in overlapping territory with the old area codes. My Cambridge number is 617, but my neighbors each have 857 numbers issued after the switch. So those people have to use ten-digit dialing, because it's too confusing to tell them that they have to use 1- for one neighbor but not the other, based only on whether they share an area code with the phone originating the call.

In the long run, it'll be a more rational system. In the short run, I'd bet it's contributing to your problem.

Edward Kmett said...

You can blame that on the expansion of valid area codes.

Originally in the north american numbering plan the middle digit of an area code (npa) was 0 or 1, while the middle digit of an exchange (nxx) was 2-9. They had to expand them, so this old rule was broken, and that apparently interacts with 10-digit dialing badly for you.

I'll admit I'm tempted to pull down a current copy of the database and find out how many of them are local calls to each other like yours to see how common this problem is.

David Feuer said...
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