Can i chane the at&t thing on my sony ericsson?

i have a sony ericsson and when i turn on my phone
at the top it says AT&T.
can i change that to like, crystal!
or something, or do i have to keep the
AT&T
cuz on other phones you can change that
and i was woundering if i could on the
Sony Ericsson by AT&T


thanksss<333333333
 
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