I have three lines of xfinity mobile. I know Xfinity mobile now supports BYOD. I want to switch one line from an android LG X Charge to an unlocked Iphone 6s plus that I already have.I have tried switching the sim card. There are two problems, phone only shows 3G connection and voicemail does not work. When I went to the xfinity store, the rep said that I would not be able to keep the number if I changed the device. Is this true? Is there anyway to switch the device without losing the number?