T-Mobile head honcho John Legere’s assuring its BlackBerry-toting subscribers they’ve got nothing to worry about despite the companies’ falling out. But, just in case they are worried, or just want to try other platforms, he’s also offering them a $100 credit toward any device. Legere made the announcement in an open letter, where he also reminded folks they can also open a new T-Mobile line for a BlackBerry if they bring their own unlocked device.