iphone 6 give a warning that sim card not supported kindly advise

Hello ~ Click on the link below and work through the steps there…

If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad - Apple Support

You may then need to reach out to your carrier. I hope this helps.

~Katana-San~

You're going to need to get a new SIM card from your carrier or a carrier in your region. Basically, you need to reach out to your carrier to resolve this issue.