My iPhone is not recognizing my sim card

My phone isn’t recognizing my sim card

it shows no service or invalid sim or no sim

I have rebooted it and brought out the sim and put it back several times and it still isn’t recognizing

and now it’s just showing no sim

and I don’t know what to do

please what do I do and why is this happening

my friend said it might be partial contact because the phone has fallen a few times