I have tried many things, the closest I can get is to edit your BBM ID details, but not the BBM id itself. If BBM developers provide the Sign In feature, I'm guessing they completely forgot about the Sign Out feature. They might work their ass of and forgot about this basic foundation.
Anyway, after suffering trying this and that, what I can tell you, the only way to do this is by re-installing the app and do all the initiation steps all over again.
