[top: A promoter display the Acer F900 smartphone during its launching in Singapore on April 22, 2009.]

TODAY'S smartphones can make you feel dumb if you are not that tech-savvy.

Crammed with features, many of these devices can "push" e-mail to you, let you watch a YouTube clip, double as a global positioning system navigator and more.

The result? Your next bill from the telco could spring a surprise.

That is because the above features gobble up megabytes - which you pay for - if you had not read the manual and learnt to turn off functions you do not need.

Ms Lee Bee Wah, 40, an MP for Ang Mo Kio GRC, recalled how she chalked up a $1,700 phone bill in four days while travelling in Thailand, four years ago.

Her Internet-enabled phone kept downloading e-mail messages even though she avoided opening them.

"I knew checking e-mail on my phone is expensive while travelling, so I went to the Internet cafe every day," she said. "I was shocked to see the phone bill later."

She found out later that she needed to deactivate the pushmail service she had subscribed to if she wanted to stop e-mail downloads.

For all three telcos, M1, SingTel and StarHub, such services are contributing more to their total earnings.

But such data-heavy services are typically costlier than voice calls. So smartphone users are more vulnerable to high phone bills.

Ms Faith Lee, a 31-year-old private banker, did not know that the financial websites she surfed on her Sony Ericsson smartphone were data-heavy, and she ended up with a $600 phone bill. "I stopped surfing those sites after that," she said.

The new breed of touchscreen phones can also be activated "accidentally".

Freelance writer Alfred Siew, 35, had one such experience while travelling in Hong Kong in February.

While in the hotel lift, he thought he heard piped music. Back in his hotel room, he heard the same song and knew he had accidentally activated his HTC Touch touchscreen phone.

His telco statement later showed that he had been online for seven minutes, playing YouTube videos. His bill was $400.

"I usually lock my phone, but must have accidentally turned it on and clicked on the YouTube application while it was in my pocket," he said ruefully.

Phones such as the Apple iPhone, HTC Touch and Blackberry are in fact seen as money spinners for telcos, said analysts. They provide easy access to the Internet, and have increased demand for data services.

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