I have an iphone xs max brought to me from New Zealand and it has face ID issues. I am in Istanbul, can I replace it here with another iphone?

Limited 1 year warranty is valid in the country you bought that iPhone.

So, you can try in Turkey, bearing in mind that Apple stores or authorized service providers might refuse to help you.

As far as Face ID problems are concerned, see these support articles:--> If Face ID isn't working on your iPhone or iPad Pro – Apple Support, and/or:--> If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support

Regards

Giulio

You're welcome, Hoda.

If you already tried (to no avail) all the steps provided in the two articles I posted in my previous reply, I suggest that you contact Apple Support directly, using this link:--> Get Support , or make an appointment and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> Apple – Location Selector

After checking it out, they'll give you all the available options.

Regards

Giulio