Hmm, I thought using Paypal account for a subscript is a requirement. If it is a Paypal subscription you can simply log in Paypal and cancel it yourself, and I can help to cancel that too.
But I never know you can set up one using a credit card without Paypal, are you sure it is a subscription? If so, maybe call your bank?
If you need further help, feel free to email firstname.lastname@example.org, provide further information on the account name, etc so we can help on this.