Nguyen Huy Hoang was not amused when he received his phone bill.
Hoang had registered for his account to be locked when the bill went beyond a stipulated amount. His bill for the earlier months were between VND500,000-700,000 a month before that.
He checked with MobiFone and found out that his number had sent a message every second through four days to the switchboard 8777.
Hoang requested MobiFone to explain this phenomenon and while waiting, had his bill surge to more than VND20.6 million as of March 20 with 1,337 messages sent to the same switchboard.
Hoang had registered for a spending limit of VND5 million, thus his account should have been locked already.
An investigation by Thanh Nien found that the MobiFone system cannot lock an account after it spends beyond the limit the subscriber has registered for.
A MobiFone insider, who refused to be named, said "to check online the spending of more than 30 million subscribers is beyond the capacity of mobile service providers."
The checking is only done around once a day, the source said. That means if an account spends beyond the registered limit, the tracking system will found out about it only after one or two days.
In Hoang's case, MobiFone suggested that the cell phone had been attacked by a virus, so they would only charge him for one message to 8777.
Hoang said he had earlier let his friend send one and only message to 8777 asking for information on lottery results.
Vo Do Thang, director of the network administrative center Athena, said the messages could have been sent constantly under the order of a hacker, if the phone was a smart phone such as Palm Pre, Nokia N900, iPhone 3GS, BlackBerry Bold, Samsung Omnia, Google Nexus One, or HTC Hero.
Otherwise, the problem could be an error of the provider, Thang said.