Verizon Wireless’ new music service for mobile phones was unveiled with much fanfare last week. But it comes with a catch: those signing up for service will give up the ability to play MP3s on their phones. The company’s new song download service, announced at the Consumer Electronics Show (CES) in Las Vegas, is being built around Microsoft’s digital-media technology. As part of that service, Verizon decided to eliminate the phones’ previous ability to play MP3 files, hoping to keep the phones’ music features simple, a company spokesman said. In most cases, customers can still transfer their own music to the phones, and many may not even notice a difference. Microsoft’s Windows Media 10 software will automatically make a copy of MP3 songs on a computer’s hard drive and load them onto the phone in the correct Microsoft-based format, leaving the original unchanged. But that software is only available for PCs.