When buying a SIM card tray for the iPhone 7, it is important to make sure that you are buying an original part. There are many counterfeit SIM card trays on the market that may not work properly. You can usually tell if a SIM card tray is counterfeit by the price. If the price is too good to be true, it probably is.
Here are some tips for replacing the SIM card tray on your iPhone 7:
If you are not comfortable replacing the SIM card tray yourself, you can take your iPhone 7 to a local repair shop. They will be able to replace the SIM card tray for you for a fee.