$50 insufficient funds from a non-active credit card?????

Has anyone else receive an outrageous $50 fee for a credit card not going through when signed up for automatic payment? The card I set up for automatic payment was not active anymore. I didn't realize I had this card on the automatic payment for Cox. Normally, if you try to use a card at a store and it's not active, the clerk tells you something like, "I'm sorry but the card didn't work." not, "I'm sorry that your card didn't work so pay me $50." How is it legal to steal $50 from someone just because their card didn't work? I wish I had never used autopay through Cox. This is a warning to others, DO NOT USE COX'S AUTOPAY. Any mistake you make is, apparently, a $50 fee.