iPhone 6S wont turn on or charge

I lost my charger a few nights ago and my phone eventually died. When my phone was dead it wasn't displaying any battery symbol but I just thought my phone was drained and thought nothing of it. I left it dead overnight until I found my charger the next morning and the phone would not charge at all, didn't even display the battery symbol when a phone is dead. I've left it on charge overnight for two nights now and its showing no indication of charging and isn't turning on at all even after trying a hard reset, soft reset and even trying to put it into iTunes to restore. My phone is completely unresponsive, please help xx