The 192 directory enquiry service is being phased out

The existing services run by BT - 192 and 153 - are being phased out later this year.

The Number already employs 500 people at its Cardiff Gate headquarters.

The Number is one of several firms offering directory enquiries following the deregulation of the domestic and international enquiry services.

Last week, an Irish company which also has call centres in Cardiff and Swansea, launched its rival service 118UK Ltd.

The Number is now planning an open day for potential employees on 3 April at St David's Hall in Cardiff.

Consumer choice

In December, the telecommunications watchdog Oftel removed BT's monopoly in the market, and the 192 service will be phased out by August 2003.

The 192 number currently receives an estimated 600 million calls each year.

Consumers now have a choice of which directory enquiries service to use.

Firms offering rival services include BT, British Gas, One Tel and Orange.

However, recent research has predicted a third of all call centres in the UK would close in the next two-and-a-half years, with the loss of 90,000 jobs.

Managing director of Mitial Research, Mike Allen, said the lower end of the call centre market would move offshore.