Unlocking & using a blocked ime

I'm just curious, after doing lots of internet research, and hearing people's complaints, could you please answer this question for me?

If an insured USA AT&T Samsung Note 4 or Apple Iphone 6 is reported lost or stolen which is under AT&T contract, and the insurance company pays out on the claim, does the lost Phone's IMEI number become "blocked"?

If so then I would like to know the possibilities for unlocking the blocked phone & use it in India.