Account Settings

I am attempting to change my account settings/cancel my subscription, but due to having put in an e-mail that is not mine, or rather a non-existent one, I cannot cancel my subscription, or alter any of my settings for that matter, as account set up is incomplete, and I really don't want to face a high billing charge for a subscription I barely use. What should I do and how can I regain access to my settings to cancel my subscription?