Does anyone know what a red circle on the phone icon means?

[iLoveiPhones]

Hi everyone,
I have a quick question. I'm here with my aunt where there isn't that much service. I went on 3G and this red circle appeared on the phone icon. Does anyone know what this means?

Thanks in advance!

 

[Jeremy]

A missed call or voice mail. Usually it will have a number in that red circle but I know with my girlfriends iPhone on Tmobile hers just pops up with a red circle and no number. I think that's because she does not have visual voicemail. Have you set voicemail up yet?