I have a mophie battery case for my iPhone 7+ and a vent charging base. They both use magnets to align and hold the phone on the base. There are no problems. Your debit card won’t be affected by the phone either. There are cases which hold cards and the cards are fine too.
What type of problems? As @Ebok mentioned there are magnets inside of iPads, that’s how the device knows to turn off the screen when the smart cover is closed..