Try this form https://subscription.blizz.com/checkout/customercare
Dear Abdullah,
Thank you for your feedback.
Have you sent us a feedback requesting the termination? If this is the case you must have received a Ticket ID, please feel free to reply there to check its status. Otherwise in order to Manage and terminate your Subscription, please go to the below link and access with the email address given for your invoicing and your password:
https://subscription-eu.blizz.com/account_login.html
Should you have any further questions, please feel free to submit your question through the above form.
Thank you for contacting us and have a lovely Monday.
Sorry for the delay caused by the holiday season. Don't worry, someone will get back to you and you won't loose money if the delay would be a reason.
The correct way to contact us for that kind of questions is to use this form and choose "I have a question about the shopping cart ...". I assume you have done that, so please be patient.