asterisk AKA "star" doesn't work!

Dear Friends, Just got the I-phone and when I call my job to check my work voice mail, I have to press ** to access my voice messages. Well on the new I-phone, ** doesn't work? My friend at work who has the older version I-phone has no problem doing this. I even tried other new 3G phones and it didn't work either. Is anyone else having this problem? Is it is software issue, At&T network issue, or what?

Thank you so much for any information or suggestions you might have. Peace, love, and respect, Prince77