Have a high school or college student on your family cell phone plan? If so, you need to know why more and more of them are blowing through mom and dad's data plan and piling up huge monthly bills.
In many cases, they don't realize they are doing it.
It's a phenomenon some have called "phantom data use," where a phone uses up expensive data when you think it's on free WiFi.
That's what happened to Nick Sachs.
"We had reached our data limit, and we have a very high data limit," he said, "and I was very shocked we could possibly reach that, because our son is always on WiFi, and he's never using the data."
Sach's teenage son thought he was watching videos on the family's WiFi.
Until the bill arrived.
"He used an unbelievable 12 gig of data in 15 days," Sachs said.
Sachs called his carrier and found out that when WiFi signals are weak, many phones will jump over to the 4G LTE data network. "What they told us was that with the newer iPhone, the phone -- whether you are on WiFi or not -- is gonna pick whichever is faster if the signal is bogging down."
So how can you protect yourself, or your kids, from going over on your monthly data allowance? It's easiest is to switch off "cellular data" when you are home, but then you have to turn it back on whenever you go out. So a better option, Sachs says, is to turn off data for just certain applications, like watching videos.
"You can turn off just certain applications," Sachs explained. "So he could turn off Netflix so it will never use cellular data, and turn off the music as well, so it won't use cellular data."
A lot of parents may soon be thanking him for that tip. The biggest cause of this happening, according to phone blogs, appears to be watching movies on your phone. If the WiFi gets weak, your phone will switch over to the data network to keep the movie going, and you won't even know it happened.
So check those settings so you don't waste your money.