Chosen Solution
Reset and powered off several times. Iphone4 working fine until prroblem found. Any help, please??
since it’s a brand new phone, i would go to the next apple store. sure - it has nothing to do with fixing stuff on your own - but this phone is new and nobody knows what bugs are showing up in a few month, since non warranty repairs/replacements are pretty pricey - i wouldn’t tinker with it more than checking the slot/sim card. and don’t forget - it’s possible that the sim card died
Try using a pencil eraser to clean the contacts of the slot, and the card. If you don’t feel like opening it, you could try to use a toothpick to check for any debris in the slot.
