How do I troubleshoot SIM card errors on my phone?

1. Check to see if your SIM card is properly inserted into the phone.
2. Power down the phone and remove the SIM card. Check for any visible damage to the card (cracks, scratches, etc.). If any damage is present, then contact your carrier and request a replacement.
3. If the SIM card is in good condition, reinsert it, then power the phone back on.
4. Ensure that the cellular data is enabled on your device.
5. Restart the phone after a few minutes to check if the SIM card error has been fixed.