Sim not supported

Contact your carrier

1. See if your carrier offers unlocking. Only your carrier can unlock your iPhone.
2. Contact your carrier and request an unlock. Your account might need to meet requirements for unlocking. After you submit the request, it might take a few days to complete. To get your request's status, contact your carrier.
3. After your carrier confirms that they unlocked your iPhone, follow the steps below. 

If you have a SIM card from a carrier other than your current carrier

Use these steps to finish unlocking your iPhone:

1. Remove your SIM card and insert the new one. 
2. Set up your iPhone again.

If you don't have another SIM card to use

Use these steps to finish unlocking your iPhone:

1. Back up your iPhone.
2. After you make a backup, erase your iPhone.
3. Restore your iPhone from the backup you just made.

Get help

You might see this message in iTunes or on your device: "The SIM card inserted in this iPhone does not appear to be supported. Only compatible SIM cards from a supported carrier may be used to activate iPhone. Please insert the SIM card that came with your iPhone or visit a supported carrier store."

If you see this message, use these steps:

1. Restore your iPhone to factory settings.
2. Contact your carrier to make sure that they applied the unlock in their system.
3. Restore your iPhone from a backup.

How to unlock your iPhone for use with a different carrier - Apple Support

https://support.apple.com/en-us/HT201328

Did you complete the process as outlined below?

How to unlock your iPhone for use with a different carrier - Apple Support