A Computeractive reader was charged £121 after signing up for a free trial of Apple’s Mobileme service, and was then given access to another user’s account.

Tom Defty signed up for the free trial, entering his credit card details as required, but was then shocked to see that his card had been charged £121.

The service’s terms and conditions warn that Apple may pre-authorise credit cards, but say that the charge is “typically the equivalent of one US dollar ($1USD)”.

More shockingly, though, when Mr Defty attempted to use the service he found that he was automatically logged into another user’s Mobileme account.

“When I went back to the site I was logged in as someone else”, he told Computeractive. “I was concerned, as it gave me access to someone else’s emails, contact lists, photographs and even backups.”

In a statement, Apple said that it had “identified and resolved an issue that caused an incorrect temporary authorisation hold on some members’ credit cards when they signed up for a Mobileme trial account. We want to apologise to those customers who were inconvenienced and are extending their trial period by another 30 days."

We asked Apple about the security of the Mobileme service in light of Mr Defty’s experience, but we are yet to receive a comment.

Meanwhile, Mr Defty simply wants to leave Mobileme.

“I’m still waiting for Apple to cancel my account, and to return the money to my card. The most annoying thing is that there’s no contact details so I can’t call or email them.

“The whole thing is a mess – it looks good on paper, but it just doesn’t work,” he said.