U.S. Cellular is trying to make it easier for mainstream and business users to manage their allotment of cellular minutes by introducing an overage protection plan.

The free service works by sending customer san SMS message when they have reached 75% of their minutes or text messaging allotment. It also sends an SMS message when users have reached 100% of their allotted minutes or texts. The messages also include the date and when a user's billing cycle ends.

The service calculates usage on a nightly basis and sends notifications the next day during business hours. The carrier said the service could be particularly useful for customers with multiple lines such as family plans or business plans. U.S. Cellular subscribers can add the overage protection plan by going into retail stores, calling customer service, or visiting their account on the carrier's Web site.

"It's a free, simple ,and efficient way to help our customers manage their cell phone use and stay within their budgets," said Alan Ferber, VP at U.S. Cellular, in a statement. "They can feel safe knowing they won't be surprised when their bill arrives."

The plan comes as there is mounting speculation about the future of U.S. Cellular, which is reportedly facing pressure to sell. The regional carrier has more than 6 million customers but it doesn't have the resources to fully compete against AT&T, T-Mobile, Sprint Nextel, and Verizon Wireless. U.S. U.S Cellular uses CDMA technology for its network and services, which is the same technology that Sprint and Verizon use. Verizon's $28 billion purchase of Alltel in 2008 shows it is willing to grow its base through acquisitions, and Sprint could shore up its postpaid subscriber base with a U.S. Cellular purchase.