Has to be worth a try Mike.
Either way he will end up having to call CS as cancellations can't be done On-Line AFAIK.
I know it can be a pain if he has had a bad experience with CS previously but maybe this time when he calls tell him to ask to be passed to "retentions" as the problems over transfer have now become a possible or even probable cause for cancelation.
This may well get the CS rep to address the problem with a better attitude especially if he remains firm but calm and polite when making the call.
EDIT: Extra tip when calling any company known to have issues with queues use a hands free/sweaker phone option if you have one. This helps to retain your cool while waiting to be connected and remaining calm often gives you the upper hand when you finally get through.