Two weeks ago, AT&T has announced the launch of a new directory assistance service available throughout California. The service, AT&T 1-800-YellowPages, gives consumers free access to business listings while providing advertisers the opportunity to reach buyers at a critical moment in their purchasing decisions.

“[The service] works like an audio Yellow Pages to give callers free access to local and nationwide business listing information from any phone,” said David Huntley, senior vice president of AT&T Customer Information Services, in a press release.

“We received positive feedback about 1-800-YellowPages during our recent market trial and are excited about expanding this service to California residents. For area businesses, we’re helping them reach potential customers who are in need of a service and are ready to make a purchasing decision.”

A caller who dials 1-800-YellowPages is able to receive a listing for a specific business, or listings for a type or category of business. They will hear short audio ads before receiving the number or, when available, before being connected directly to the business that they select. The service is accessible from landline and any mobile phone.

Although it was not explicitly mentioned in the release, writes Greg Sterling in his Screenwerk blog, PPCall [Pay Per Call] is the primary ad model in the new AT&T offering. Indeed, mobile is really where PPCall is starting to take off. Google, Yahoo! and Microsoft are also all now offering PPCall advertising on mobile devices.

As all the major carriers and search engines attempt to develop mobile local search and mobile search capabilities, the average person is already familiar (and comfortable) calling Directory Assistance and will likely embrace such services with open arms.

Voice is a much more intuitive and, in some ways, efficient interface than those otherwise available through the phone keypad  even if it’s a full Qwerty keypad, Sterling added. We are likely heading to a very segmented mobile local search market where some people use mobile search on smartphones, some use SMS query systems, and some use voice and Free-DA offerings. In the end, ease of use and efficiency will determine which of these will prevail.