Operator Jingle Networks of 1-800-FREE411 has sold out its inventory of sponsorship ads for the year.

The company hosts two ad spots per phone call made — one for national sponsors, and another for local/targeted ads.

The national sponsorships are 10-second audio spots that callers hear before receiving directory assistance from local brands like AMC Theaters, Earthlink, Cablevision, McDonald's, and Miller Brewing.

The company fields 20 million free directory assistance calls a month, up 18 percent since March, according to TechCrunch. Last year Skype partnered with Jingle to bring the service to its users.