Sofia Rubenstein, 17, got in trouble the way a lot of teens do these days.

Her incessant text-messaging racked up a huge phone bill on the family's wireless plan.

"It's whatever pops into my head. There's no stopping it," she said. "Sometimes I'll be on the phone with someone and I get texted, and then I'm having two conversations at once."

Last month the Washington high school junior used 6,807 text messages, which, at a rate of 15 cents apiece for most of them, pushed the family's Verizon Wireless bill to more than $1,100 for the month. Sofia knew she'd been texting a lot but couldn't believe the "incredible" number she hit. "I just thought, oh my God, my life is over," she said.

Indeed. Sofia will be working in her parents' retail store this summer to pay off her debt -- but she definitely won't be the only teenager paying for text abuse. Minutes? Forget minutes. It's all about the text allowance. It needs to be supersized, now that instant messaging has leapt from the desktop to the mobile.

Families who carefully researched their wireless plans to cover calls with no extra fees are discovering, to their horror, that their thumb-tapping teens have found a new way to blow the budget. In Sofia's case, her parents' plan included only 100 free text messages a month -- fewer than half of what she was using every day "at all points of the day" -- and she racked up massive per-message fees fast.

Teenagers elsewhere in the world have been texting furiously for years, using the cheap technology to evade government controls on dating in Saudi Arabia and to foment revolution in the Philippines. Now that texting has exploded in America, it's regarded as one of the current teen generation's inexplicable behaviors, like instant-messaging or spending hours on Facebook.

"What we have to see is that connections are very different than when we were growing up," said Lilli Friedland, a Los Angeles psychologist who also does consulting for the entertainment industry. Text-messaging, she said, is how kids feel comfortable communicating today. Think it, text it, keep it short, have to have it.

Parents seem to accept this new reality and are switching to wireless plans that allow unlimited text messages, which pile $10 to $30 a month on top of an already hefty expense that didn't even exist a decade ago. Janet Boyd, a lobbyist for Dow Chemical, said she and her husband "nearly died" when they got a $70 charge for their 20-year-old daughter's text-messaging. They went to an unlimited plan. "Seventy dollars is a lot more than 20," she said.

Wireless companies, meanwhile, are rolling out new packages to meet demand. "For a teenager to send thousands of text messages a month is not unusual," said John Johnson, a spokesman for Verizon Wireless. Last month the company introduced an unlimited texting plan because even its highest bundle of free text messages -- 5,000 a month -- wasn't enough.

Market research indicates the consumers mostly likely to send and receive text messages are those between the ages of 13 and 24. Last year, 158 billion text messages were sent nationwide, nearly double the number in 2005, according to CTIA, the Wireless Association. With that kind of growth, texting will continue to be very profitable for wireless companies, said Roger Entner, senior vice president for the communication sector at IAG Research, even with bundling plans to lower consumer cost.

The strife this popularity is causing with family phone bills is on display in a popular television commercial for AT&T Wireless to promote its new unlimited plan. A young girl is confronted by her mother for her text-messaging charges, and the girl answers in "text," saying "o-m-g, i-n-b-d." Subtitles provide the translation: "Oh my gosh, it's no big deal."