Ever vigilant cellphone operator Vodafone upgraded its voicemail software this week to provide improved security. Security was improved to the extent that a sizeable chunk of users found themselves locked out of their own voicemail.

Slothful punters who had never bothered to change their PIN numbers from the original '0000' or '9999' were unable to listen to vital messages such as 'I'm on the train'.

A Vodafone spokesman - who rather engagingly couldn't tell us how many users the company has - reckoned that around 45 per cent of customers used voicemail on a regular basis.

"We put notices that we were upgrading the system in the bills," he explained, "But anyone who hadn't changed their PINs was, unfortunately, locked out." ®