If the card is a magnetic stripe card with a long black stripe on the back, find a magnet with strong magnetic force and put it on the magnetic stripe for a few minutes, and the magnetic stripe will naturally degauss. If you don't trust me, take a knife or something, physically damage it, and scratch it a few more times.
If there is a chip on the card, you need to carefully pick it off and smash it with a hammer, and the chip will be broken. Then stick it back.