Report lost or stolen credit cards immediately. Sign the back of your new card as soon as you get it. Make a list of all your cards and their numbers. Keep the list at home. Carefully check your monthly statements.
Mistakes can happen.
Never give your credit card number over the phone unless you are dealing with a well-known company or you called them first yourself. Checking monthly credit card statements. Mistakes happen and if you're being charged for something you don't recall, talk to the card company - there's a customer inquiry number on each month's statement. Keeping cash at home. With credit and debit cards easily at hand, try not to keep large amounts of cash at home.