I'm using an Iphone with firmware 1.1.1 and my voicemail button works perfectly i.e when i press the button it dials voicemail its just when i miss a call on the phone and someone leaves a voicemail I have no idea as this seems to be AT&T linked and I'm using T-Mobile in the Netherlands.
Is there any applications that at least lets you know when someone has left a voicemail? anything out there?
There are alot of us on the same boat as you. As far as I know, there isn't anything yet... Some say the new firmware 1.1.2 fixs the sms (flash) issue, so that might fix it....
if you will you can change your voicemail settings such that t-mobile calls you when you have a voicemail message. the annoying thing is that if you do not answer that call it will keep calling you untill you do (rather than a sms that comes in only once)