Activating Voicemail button on my unlocked iPhone
The only two features that were not working on the iPhone that I won and subsequently unlocked on the O2-UK Network last week were the YouTube application (which I have no want to fix but there is a solution) and the Voicemail button within the phone part of the iPhone.
Gizmodo reposted a quick and easy fix that was originally released by the iPhone Dev Team. For O2 users simply call this number from your iPhone:
Now when you press the Voicemail button it will call your Voicemail inbox, no visual voicemail unfortunately. Simply replace the
901 with any other service providers voicemail number if you require.