Hong Kong - Mobile phone users in Hong Kong who go online are being hit with hidden charges of up to 1,800 US dollars a month, a consumer watchdog warned Tuesday.

High-tech phones that can receive e-mails and data-switch between networks sometimes lock onto paid-for wireless services without the phone owner's knowledge, the Hong Kong Consumer Council warned.

The watchdog said it had received 143 complaints about unexpected charges for internet services between January and May and 270 in 2007.

Bills can be particularly high in cases in which people use their mobile phones to download large data files, which phone companies charge for in terms of volume, the Consumer Council said.

One complainant racked up charges of 14,000 Hong Kong dollars (1,792 US dollars) in one month when his service provider connected him to the internet through its fee-paying service without warning him first, the council said.

Hong Kong is one of the world's most advanced cities in terms of high-speed internet connections with free wireless connections available in the airport, on street corners, around government buildings and in many bars and restaurants.

The government is also considering plans to make the city of 6.9 million a fully wirelessly connected zone with "WiFi" signals available in every building and apartment block. (dpa)