The UK's £700m directory enquiries market will open to competition in mid-December, with the existing 192 number phased out by next August.
The Number - the UK brand name of US firm InfoNxx - is to lavish £16m on a launch marcoms campaign.
Le Fevre Communications was hired in September on a B2B/trade PR remit.
It is understood that JCPR and Le Fevre will share a PR budget that could stretch to almost £1m.
The Number, with UK offices in London and Cardiff, is recruiting more than 1,000 staff for three call centres, the first of which will be in south Wales.
In addition to a directory enquiry service, The Number plans to offer information on travel and leisure services such as train and cinema times.
Chris Moss, who was marketing director at telecoms giant Orange from 1993 to 1995, joined The Number last month as European chief executive.