Somebody called my girlfriends cell phone one day and changed her voicemail greeting. Obviously she didn't realize you had to change the initial pin # when setting up the voicemail. Neeedless to say, It was quite graphic.
Here's how you do it......
Call a cell phone, if no body answers and the voicemail greeting starts press the star * key, afterwards hit 1111 and see what happens. If the voicemail box pin has never been reset with a new pin then you will have access to all the changes on the cell phone voicemail.
I do not suggest anybody do this sort of thing but it's kind of funny.