The Nokia Lumia 620 has a secure method of storing your SIM card in your smartphone. The SIM card sits beneath the frame of the device, underneath the battery.
However, it needs some nimble fingers to extract the SIM-tray holder and to replace it. Once you have carried out the action one or twice, it will become second nature to you.
Gently slide the sim-card tray from beneath the phone panel. It can be completely removed without damage to your device.
Place your sim into the sim card holder and replace the sim card in your device. Replace the battery and the cover of your phone.
Your phone is now available for use.