IPhone 6 Completely Stopped Working

My IPhone 6 suddenly shut off and is stuck on a black screen, it doesn't charge, make any noise or vibrations, can't connect to Itunes. I've tried holding the power button for 10+ seconds, as well as the power and home button too but the screen stays black.

It was on around 80% battery when it died, I was having issues with chargers staying plugged in and charging but once it was at 100% the phone lasted a good amount of time.

I also got this phone as a replacement when I went into Apple 7 months ago as my IPhone's battery couldn't hold a charge so they gave me a refurbished one.

Any help would be much appreciated, thank you.