[H] Blackberry>>My Display

[Winterlight]

I have a AT&T Gophone account that I use for Craigs list adds, or 
service calls, to shield my primary cell phone account.I have been 
using a Cingular Razar for this purpose but a friend gave me their 
old Sprint Blackberry Bold 9650. It wasn't locked. I cleared old user 
data and reset the phone. Then I installed my AT&T Gophone simm. Then 
I went into settings and changed the simm number and setup voice mail 
to call AT&T. It all works as it should. Caller ID, voice mail, wifi 
everything.

 However, when I use the phone, up at the top of the screen I see 
AT&T the time and underneath it I see My Number only it is the old 
Sprint number.I have looked at all the menus, downloaded the manual, 
goggled it extensively, but I can find nothing that tells me how to 
change the display at the top of the screen   to the AT&T simm 
number. Anybody know how to do this? Thanks w