Well actually...They do..
At&t DOES send messages when the usage is too much. There is a High Usage Team that makes two attempts to contact people for intl usage. Normally they will send a Txt twcie advising you to call a certain # that goes directly to the high usage team so they can deal with the usage BEFORE it appears on the bill. If you are using a laptop with a data plan, I beleive they e mail the address on file.
La Grange, IL
This one was probably way too busy surfing and sending pictures to bother even looking at text messages.
But don't bother interrupting the punditry here with facts. Just makes 'em crazy having to think that hard.
Toolmaster of La Grange.