-Mobile is taking a leaf out of the tech industry book and separating phones from their numbers.The company's Digits service will allow you to pick up calls from any device  in much the same way Google does with its voice service and Apple does with its AppleID. It will launch on May 31.The service has been in beta for roughly six months and represents a significant shift for a phone company, given that the single-number-to-single-device has been the foundation of the industry's economic models.Customers' existing numbers will be "upgraded" to the new Digits service and can then be extended to...