According to AppleInsider, Apple released carrier update for Verizon to help to eliminate issue about cellular data being used awhile Wi-Fi network is on. The update has to go through manually with over-the-air and instruction. For full detail, click the link below.

 

 

http://appleinsider.com/articles/12/09/30/iphone-5-carrier-update-fixes-bug-causing-cellular-data-use-while-on-wi-fi