Oh, woe is you when you try to cancel them. Cutting them up doesn't do the trick. Calling and canceling doesn't either. I've had a card company rep argue with me over the phone that I could not cancel, even though there was zero balance. I did eventually get that one canceled but what a hassle.
Sit down, right a letter to each one, provide your account number and your signature, send it via U.S. mail, "return receipt requested", ask for a letter from them via U.S. Mail, verifying that they have indeed canceled it. By law they have to provide that upon request.
If they tell you over the phone that they have canceled it, chances are great that they are lying to you and you will learn of it the next time they send you a solicitation to buy "credit card protection" for your account, mentioning the last 4 digits of the account you thought you had canceled.
Then alert the credit bureaus that the accounts are closed, because most likely the credit card company won't do it.