iphone voicemail settings missing

Hi,

I have an iPhone 4 on the UK 3 network. I currently do not have visual voicemail setup and have to call the number 333. When I get a voicemail as soon as I unlock the phone, it automatically starts dialing the 333 number without my permission. Its extremely annoying, there's nothing I can do to prevent the phone calling my voicemail when I unlock it which uses up my credit instantly.

I have searched online and cant find anyone else having this problem.

I tried to set up visual voicemail instead, however when I go to settings->phone, I find there's no voicemail page. Everyone else repots having a voicemail settings page under settings-> phone, but mine appears to be missing.

Again searching for iPhone missing voicemail settings' shows nothing

What's going on :S?