AirTouch Cellular has launched a wireless service that allows laptop computer users to tap into the Internet and send files using a digital mobile phone as a modem. AirTouch Cellular, a subsidiary of Vodafone AirTouch, is selling the service in its Seattle, Salt Lake City and Michigan markets. The company said it plans to offer the service in the 25 states where it sells mobile service--including California--by early next year. The service, called Net Access, requires a special Qualcomm digital phone, which sells for between $69 and $150, and a cable to link the phone and laptop. Per-minute rates for data would be the same as for voice calls, plus a $4.99 monthly fee. Files are transmitted at speeds up to 14.4 kilobits per second, faster than the average 9.6kbps speed for most wireless data services. Metrocom's data-only service, called Ricochet, provides access at speeds up to 28.8kbps, but that service is only in limited areas and requires special equipment.