The prefix, formerly used by Shinsegi Telecom, which was merged into SK Telecom in 2002, is somewhat unexpected given that all new mobile subscribers today use a number with a 010 prefix.

It's because Cheong Wa Dae in the late 1990s purchased a number of cell phone numbers for its staff from Shinsegi Telecom.

As the mobile operator built many of its base stations near military bases, the police, the military and other agents of the country used to subscribe to the operator, a telecommunications industry official said. The president's mobile phone number was also purchased in those days.

When subscribing to Shinsegi, Cheong Wa Dae secured its own exchange number starting with 7. This means most of its phone numbers are 017-7XX-XXXX. Upon leaving Cheong Wa Dae, staff handed over their number to their successor.

"When calling amongst themselves, they don't need to enter 017 and the following 7XX. They can reach each other by dialing just the last four digits. This service is available for group subscribers such as big enterprises," the industry official said.

However, it seems Cheong Wa Dae won't be able to keep the 017 prefix much longer, as the Broadcasting and Communications Commission plans to integrate all prefixes into 010 as soon as the number of subscribers using the prefix surpasses 80 percent of the market.

The telecommunications industry expects to reach that level next year. It currently stands at 55 percent. When the 010 unification policy is put into effect, Cheong Wa Dae will also have to change its 017 prefix to 010.

(englishnews@chosun.com )