Q: I Phone 6 s stopped working completely....

Hi - My iphone 6 s was purchased in France around two months ago, other than the odd blip its been working fine. Yesterday when plugged into a car charger it had low battery, it just went blank and won't come back on. I have tried all three methods of home button and on/off button but dead. Do i contact apple through a shop and get a repair or replacement ? take to a local shop because i am doing something silly ? Can i take it to a franchised apple place ? Any other help would be appreciated ..... Oh incidentally it won't sync either and no sounds from siri....Regards Steve.