Have you checked the Beejive forums? It looks like this may be a known/recent issue, as there are a couple of threads.
I'm having a somewhat similar problem....with a previous iPhone that I have re-installed Beejive on, albeit with a different user and logon credentials.
Both iPhones are on the same AT&T account and sync with the same iTunes account, on the same MacBook Pro. The older iPhone is pulling up my old Beejive display name even though it's installed and configured for a different user. Beejive on that iPhone works for sending/receiving correctly, but the Beejive display name that shows up on other Beejive enabled phones is showing my original name used 2 months ago. My new iPhone with Beejive is doing everything correctly, including the display name.
It's like the display name is stored somewhere in their server system associated with the iPhone IMEI number (or some other unique ID identifier), and it's not changing based on the changes in the Beejive settings on the iPhone.