FaceTime not working on iPhone 6 Plus purchased from Dubai
Sorry, Facetime is not available on devices purchased in the United Arab Emirates and therefore in Dubai, as stated in these KB articles:

http://support.apple.com/kb/TS3367

FaceTime might not be available, or might become unavailable, on devices purchased or used in certain countries, including Saudi Arabia and the United Arab Emirates.


http://support.apple.com/kb/ht1937



I recommend that you contact Apple support in Sri Lanka at http://www.apple.com/lk/support/contact/ or a local Apple reseller, they may be able to help you.
To find a reseller near you visit https://locate.apple.com/lk/en/sales/?pt=all&amp;lat=6.9270786&amp;lon=79.86124300000006, press New Search:

and type in your address.