MyFreeCams does not offer subscription services, so there are no payments to cancel.
If you want to permanently delete your account, however, you can do so by entering your username and password in the proper fields on this page http://www.myfreecams.com/mfc2/static/delete_account.html?delete=1&cache_id=158&target=main, then clicking the button labeled “Delete My Account”.
Be warned that you will not be reimbursed for any tokens that you have purchased.