How to fix Nikon d3100 card slot?

It clips in the card slot but it keep saying something is wrong the card. I change it more than seven times n still the same thing. Some time it says insert card hmm please am begging for assistance. One in a blue moon it was working now it not at all.

Have you tried another card?

They're not that expensive if you don't go nuts over size (NOBODY needs 32GB on a DSLR), and you can never have too many.

It's possible that lint or dirt has gotten into the card slot. Use a toothpick and gently probe around in the slot to move or remove whatever is there.

Try another SD card.

You can't. Bring the camera to the service center.