At CTIA Wireless, ISP (Internet Service Provider) EarthLink announced plans to start selling its own brand of handhelds this spring based on Research In Motion’s (RIM) BlackBerry Wireless Handhelds. This is appears to be an expansion of its wireless Internet service for PDAs, which it started offering after it took over OmniSky a couple of years ago.

Like all BlackBerries, EarthLink’s device will feature email, voice calling, Internet browsing and a QWERTY keyboard. The difference is that instead of buying the smartphone directly from RIM or a mobile carrier, it will be sold, supported and provisioned by EarthLink.

Like other ISPS, such as Yahoo! with its recent announcement of adding voice to Yahoo! Messenger, EarthLink is attempting to offer more variety and services to its users. One of the chief selling points Earthlink it using for its devices is the leveraging of the same anti-SPAM software to block unwanted emails as is used for its desktop users.

According to USA Today, EarthLink will buy cellular network capacity wholesale. Reuters reports that data plans should range from $20 to $50, while voice service will cost between $40 to $75.