My iphone battery dies at 50 percent?

How can I fix my iphone I got it in December but I didn't buy it directly from apple I got it from koodo where my phone plan is

Your battery might be faulty or damaged, its the best to ring the shop and tell them that your phone battery is something wrong or either go to apple store ask for help or go to phone repair shop,
My phone happened like that once but not an iphone, my phone dies about 37 percent but when i bought a new battery everything gone back to normall.

How many times are you going to ask, Apple will fix it for you as it is under warranty regardless who you got it off.

Take it to an apple store

We come on here to learn how to fix it not to be stated the obvious " take it to an apple store" most who look things up like this want to do it on their own. Smh