well i ahve a 8820 with att and my neighbor has the same ... but 1 of my friends has the 8800 for t-mobile and we cant send or receiving messages thru blackberry messenger ... only me and my neighbor could do it 8820 to 8820 but we cant talk to the 8800 user ... i checked everything ... we even reinstallled the OS and it didnt work
What happens when you try to send a BBM message to the 8800 person? Does the message show with a D after you send it (which means they received it) or not? What happens when they send a BBM message to you?
Also, make sure your friend if they have a Pearl, they have their name in BlackBerry Pin Messenger without any spaces or special characters! If they do, then it does not work correctly...