Subscriber Identity Module, or SIM, cards are small data cards used in GSM-frequency-based phones around the world, such as the AT&T and T-Mobile networks in the United States. SIM cards store the network settings and information of a mobile network provider along with the personal information of the user on the card. Damaging or destroying a card may be necessary when a card has become outdated and replaced or if the card owner switches to a different network. All the information is stored in the chip located on the back of the card. Depending on the amount of damage, a damaged chip may be unable to function in a phone.
Place the card on a solid surface and smash the card with a hammer. Blunt force trauma may render the card unreadable and may keep the card physically intact.
Break the card in two. Use both hands to bend the card back and forth until the card is in two pieces. If the chip area of the card is not damaged, the personal information on the card could still be read, but a broken card will make it harder to read in most phones.
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Submerge the card in a glass of salt water. Salt water is highly corrosive to metal, and the metallic chip will slowly degrade if left in the water for a long period of time.
Cut the chip with scissors. Cutting the chip into several pieces will destroy, not damage, a chip but will quickly ensure that the information on the card cannot be read.