Boost Mobile, a part of Sprint Nextel's (NASDAQ: S) prepaid unit, is enhancing its $50 unlimited CDMA and iDEN calling plans by adding new services and debuting a new handset. The company announced today that besides unlimited calling, customers now receive unlimited 411 calls, email and instant messaging for no extra fee. In addition, customers on the $60 unlimited BlackBerry plan, which already includes unlimited email and IM, will have the added benefit of unlimited 411 calling.

The Samsung Rant, which features a Qwerty keyboard, will join Boost's portfolio of CDMA devices. The Sprint unit debuted three CDMA phones for its unlimited service in January, including the BlackBerry Curve 8330, the Sanyo Mirro and the Sanyo Incognito. The Rant will be available May 19 for $149.99.

In January, Boost decided to broaden its unlimited prepaid offerings beyond the company's iDEN network to include its CDMA network. Last year Boost debuted the $50 unlimited prepaid plan over the iDEN network and it has been a hit for Sprint.

Boost spokeswoman Danielle Alvarez told FierceWireless than the new enhancements are for both the CDMA and iDEN customers. When the unlimited plan launched on CDMA it did include access to the various email portals, she noted, but not IM, which had cost $1 per day per portal.

For more:
- see this release

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Article updated May 4 with comments from Boost Mobile.