Since you received the product and did not return it you are still responsible to pay for it. There was an offer to sell it and you accepted it by agreeing to pay for it. You are therefore guaranteeing payment for the item. The fact that the company did not accept the credit card payment at that time is irrelevant since you accepted the product. You could still pay for it by trying to submit the card again or by sending a check. If you do not pay it, they will in all likelihood seek to sue you for the price of the priduct plus interest from the date you accepted it. Your defense can not be that they sent it anyway because you never told them you would not accept the product. You merely could not pay at the time requested but the fact you accepted it later ratified the initial agreement.