I've been an AT&T subscriber since 2003, and I love the service and support -- the billing, however, has gotten out of control. We have 3 lines for our family -- I have the grandfathered unlimited data line, my wife and son both have the 200MB/month plans. We have 450 minutes shared/month -- but our rollover is close to 6000 hours now because we rarely use the service for talking.
My son just got an SMS message this morning saying that he had racked up $50 in text messages. I logged into our account to check what plan he was on. Both my wife and I are on "Messaging 200" for $5/month -- and I believe my son was on that as well, but it somehow got removed (??). I contacted customer support about adding it, and they said it was no longer available and that I should do unlimited messaging for $20/month.
Keep in mind that SMS messages use literally no additional bandwith on the network (MMS messages, on the other hand, do). There should not be any charge for this service, because AT&T doesn't have to do anything to support it. I priced out a plan with another provider, and it came to $90/month for unlimited calling and texting with 500MB/month data. I've signed up for that, and whatever penalty I have to pay for early cancellation will be made up in a handful of months. I'll miss my unlimited plan, but I rarely went over 500MB anyway.
I love everything about AT&T wireless, but the pricing has become completely ridiculous.