Andy,
try 0208 0802105
I was got this time last year
Took six months to get half the money back off ebay
The only uside was the hacker signed me up to loads of expensive ebay stuff so I got on their preferred customer list which mean't i got the phone number.
My advice is make them clear all transactions up bfore their next billing date, my problems were from being too slow to notice some of it.
Also, check they haven't signed you up for any "subscriptions" on your account!