The chairman of a U.S. Senate committee overseeing business issues asked Apple Inc to answer questions about its disclosure that it slowed older iPhones with flagging batteries, according to a letter seen by Reuters on Wednesday.

The California-based company apologized over the issue on Dec. 28, cut battery replacement costs and said it will change its software to show users whether their phone battery is good.

Senator John Thune, a Republican who chairs the Commerce, Science and Transportation Committee, said in a Jan. 9 letter to Apple Chief Executive Officer Tim Cook that “the large volume of consumer criticism leveled against the company in light of its admission suggests that there should have been better transparency.”

Apple said it will cut the price of a replacement for an out-of-warranty battery to $29 from $79 for an iPhone 6 or later. The company also will update its iOS operating system so users can see whether the battery is in poor condition and affecting the phone’s performance.

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