You should look into password enabling,to see if that stops it. remember Paris Hilton? Here's a story
Millions of cell phone users are at risk of having someone listen to their voicemail or steal their contact phone numbers and other private information, according to a report issued this weekend by an industry consulting firm.
Representatives from Sprint, Cingular, and T-Mobile confirmed the basic premise of the attack, which is possible because those services enable consumers to turn off the password-checking function.
Cell phone hacking gained prominence last month when reports surfaced that pop star Paris Hilton's T-mobile voicemail and phone book
The link
http://www.msnbc.msn.com/id/7046776/