If like me you are new to O2 then you need to remember to activate the voicemail. When I switched from Vodafone to O2 I didn’t know that my voicemail on the new O2 network wasn’t active.
To activate and setup your voicemail:
1. Dial 1750 to active
2. Record your personal greetings by dialling 901
3. Change the number of rings before it goes to voicemail by dialling: **61*901*11* number of seconds to ring followed by #. The number of seconds to ring has to be one of these: 5,10,20, or 25 seconds.
What I really like about the O2 voicemail on my iPhone is the visual voicemail. The allows me to see a list of voice messages and listen to the one I want without the need of dialling the voice mail.