If like me you’re new to O2, you must remember to activate the answering machine. When I switched from O2 Vodafone I knew that my voicemail was not active on the O2 network news.To activate and configure your mailbox:
1st Dial 1750 to active
2nd Record your personal greeting by dialing 901
3 Change the number of rings before it goes to voicemail phone: ** 61 * 901 * 11 * number of seconds, followed by # ring. The number of seconds in the ring must be one of those. 5,10,20 or 25 seconds
What I love about the voicemail on my iPhone O2 is visual voicemail. This allows me to see the list of voice messages and listen, I want, without the need for the choice of voice mail.