Lucy is O2's online avatar. You can send her a question and she'll do her best to respond in real time. I asked whether the network was down, as people were getting a 'fault' message when they dialled my iPhone. Here's her instantaneous reply:
"You are allocated an anniversary date the first time you top-up your Online Pay & Go account with £10 or more. This anniversary date is when your free 300 text messages or 75 media messages starts, and your 300 minutes of WAP allowance starts.
If you wish to keep the same anniversary date, you need to top-up your account with a minimum of £10 each month at least 48 hours before your anniversary date..."
The shame of it. I'm not even on pay and go. I have a proper contract and everything. But I like the concept of having an anniversary with O2. Provided, of course, that people are actually able to ring me between one annual celebration and the next.