I once complained about their switch to a premium rate line via their webform. Apart from receiving a 'we'll get back to you' letter shortly after, I got no response. Until over a month later, when someone phoned me and I managed to dig out of him that if you actually do have a problem with their service, you can get the cost of the phone call refunded to your account. Not something they advertise though.

This could lend some credence to the theory that the person Simon spoke to actually did change something at their end - if they can claim that you simply had to reboot it all, it's not a fault at their end, so they don't have to refund the cost of the call.