The SIM card reader inside my phone is not reading properly

I have been using an LG G3 phone for little less than a year now and recently my phone appeared with the message "Invalid Card" in the top corner. After reinserting the card multiple times the phone began to work again, then after an hour the message appeared again. I retried removing and inserting the card it now only says "No SIM" and an icon at the top of the SIM card with an X through it. I do not know if it is a hardware problem and the SIM card reader is broken or if I might need to reset the phone to fix it. Resetting the phone is not the most ideal option, nor is replacing it so I am hoping there is a way to fix it without replacing the phone. I have already tried switching the SIM card for multiple new ones but none of them seemed to work either.