iphone6 won't turn on and black screen with no more over the apple logo.

My iPhone 6 since October ,2017 current 4 months and few day ago ,I'm took from Singapore apple store ,orchard road ,Genius Bar replaced my old iPhone 6 and currently using new iPhone 6 is starting problem since iOS 11.2.2 .case of problem is wifi drop ,I'll be contact apple support chat ,they check diagnostic my ph:wifi is can't work ,I'm using bluetooth iOS 11.2.3 update after that my ph: wifi is good situation and return to work after again update iOS 11.2.5 while still work and last update iOS 11.2.6 few day later wifi is start again drop and bluetooth is spinning setting mode ,few day ago control centre wifi sign is grey out and in the setting wifi button is can't turn on ,and then bluetooth label also in setting label spinning but press turn on control centre bluetooth sign when bluetooth is on and setting label bluetooth sign is still spinning ,after one more happen auto restart stand by mode once a day 2 or 3 times and yesterday more than over 5th times ,and while income call coming not necessary press to pickup sign and automatic pickup,after that stand by mode swipe down notifications when on top red shape and a lot of drain battery and while using ph: body is over heat ,I'm turn off: cellular data and release all page after that turn off my iPhone ,after press sleep wake up button while can't on ,appear only apple logo and no more after that black screen ,I'm try half day and connect with iTunes and new update iOS 11.2.6 while down load finished appear error 1403 and can't turn on and still black screen ,I suspect quality of Singapore apple store replace my new iPhone 6 ,may be refurbish and low quality coz my old iPhone 6 is I'm using over 3 yrs not any problem ,I'm exchange battery after upgrade iOS 11 a lot of drain battery and background can't off camera mode ,they replaced current new one a lot of problem and now can't possible to use and back to apple store Singapore store ,orchard road ,Genius Bar .