In the US, you take your phone to your carrier while under warranty.
I've tried to get Samsung to repair or replace my Galaxy S6 for two months now. Finally they agreed to fix it last week. Instead they lied about what I sent and returned it. They covered their tracks by peeling off the serial number on the back of the phone and keeping the original box. The box had the IMEI number, model number, and color of the phone. They claimed I sent a phone that had a serial number that showed a black phone. The phone was blue and that color was verified on the box.
I've thought highly of Samsung until this total dishonesty on their part. My advice is to buy some other brand.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic