Carrier billing for Google Play (and Android Market before it) has been around for quite a while, providing a way to purchase apps and have the charges show up on your phone bill. Google recently expanded the functionality on some carriers like T-Mobile and AT&T to allow for books, music, and movies to be charge on phone bills, and today Sprint users can also take advantage of the feature. That leaves Verizon Wireless as the only major US carrier to not yet support carrier billing, and we haven't heard any word on when to expect it, if ever.