Can I see who my child texted on their AT&T cell phone?

My son’s been awfully obsessed with text messaging on his cellphone and I’d like to check and see what’s going on. Is he texting one person a lot, or a group of people, and are they in our local area (area code 415) or from out of area, which would suggest something more creepy and alarming? How can I tell? We have AT&T cell phone service…

First off, I would confront him and say that you’re concerned about what’s going on with his phone usage and that you’d like him to tell you who he is texting and let you read some of the texts. If he freaks out, well, that could be another sign that something untoward is happening (then again, it could also be because his buddies are sharing dirty jokes and it’s innocuous, so don’t read too much into it!)
Still, it turns out that all the major cellphone carriers actually have quite sophisticated Web sites that give you the ability to access quite a bit of information, and if his mobile device is on your account — as I bet it is — then you can pop onto the AT&T Wireless Web site and check up on what’s happening.
It’s worth pointing out that the text messages themselves are not stored on their server nor are they accessible when you view the online information. It’s just time, number, and sent/received. Still, that can be critical information about whether it’s one person (a new girlfriend?) he’s obsessed with, a text-based service like Twitter that he’s signed up for and it’s 99% received messages, or even whether it’s happening in the wee hours of the morning or just at dinner time.
Start out logging in to your AT&T account on the site and you’ll see a display that shows all the cell phones associated with the account, like this:

From left to right, that’s my teen daughter’s phone that has gotten sufficiently close to its data limit to generate a warning, my iPhone, and my own son’s feature phone.
Let’s look at his account. To do that, click on the phone image or the “View details” link and more information about that line will appear:

Typical modern kid: he barely uses the phone as a phone but instead texts a lot, 146 texts in 18 days. Actually, that’s not bad at all. I text way more than that!
On the top left of this window, notice the “View all usage” link. Click on that.

Ah, yet more information about the line. We’re closer, though. Now on the top right of this view, click on “Text/Web usage details” and you’ll — finally — be able to see details of text usage for this particular line:

I’ve blurred out the numbers to protect my son’s privacy but on your computer screen it’ll be immediately obvious if it’s one number that he’s texting a ton or a group of numbers. In this case, notice that all of these text message, from 10:32am to 2:13pm on 2/9 and again at 9:54am on 2/10 are all incoming or “received”. People text my son, but he’s not always paying attention. Kind of a relief, actually.
One of these numbers, however, is out of area for us. Area code 678 turns out to be Atlanta, Georgia, a long way from Colorado and a city that I know we’ve never visited. So who is it? Probably a solicitor or junk text, and a bit of research could show if it’s a two-way conversation or just the occasional received message too.
Let’s say it is a receive-only and that your son would be happy if it never showed up again. Some companies ignore anything you send them, so a simple “STOP” seems logical but will fail. Instead, if you’re paying the additional few dollars for AT&T Smart Limits (which I think is ridiculous, I think it should be free) you can actually block the number from sending any more messages to your son’s phone.
To do that, go back to your main page on the AT&T Wireless site. On the left, you’ll see a pop-up that says “I want to…”. Click on it and look closely:

As you can see, one option is “Manage AT&T Smart Limits”. Select it and you’ll be able to block the specific numbers. Even better, you can also effectively take your son’s cellphone offline in the wee hours of the night (or at school during Mon-Fri) with their schedule capability.
I have both of my children’s phones in parent-only-mode from 11pm to 7am every single night, actually:

In this mode you can supply a list of acceptable numbers that can call/text that particular line, so mom, dad, grandma, and even other siblings could still get through if needed, but everyone else would just have their message failed. Good for avoiding those 3am sneaky text dialogs when you think your little angel’s in bed.
Hope that helps you out with your son’s texting. It’s a blessing and a curse, this modern zeal for all things mobile and digital.