@Anonymous User
Have you got more than one username or Sky ID ?
Your quickest option might be to jump across to live chat, they can look at your account on their computer system and should be able to cancel the free trial on your behalf.
If you open the linked page below and click on the "contact us" in the green box, this will take you to a secondary page where there is an option for live chat.
Recommend using a PC, Laptop or Mac when you contact them.
http://help.nowtv.com/article/None-of-the-above-manage-my-account
