Nokia 3220 #$@%! mMode

Probably been answered a couple of hundred times, please bear with me...
I bought an 'unlocked' 3220 for use with Cingular. I can't receive text messages, media, or anything other than good 'ol voice calls. My Cingular rep took a look at it and said it is because this used to be an AT&T serviced cell phone and had 'mMode' displaying instead of 'Media'. Is there any way to convert this to 'Media' mode?

Any help MUCH APPRECIATED!