can I track or access who has used my hotspot connection as mine was "hacked"

my old iphones hotspot was turned on ( I have no idea why or how I was on holidays at the time) and someone then commenced to use my connection and run up $600+ in data charges. This phone has never been used previously as a data phone only ever calls and texts ( its like an emergency contact phone only) is there a way to track or uncover who it was that accessed it ( I suspect it was next door) and can the phone be hacked so people can remotely turn such features on as I turned the hotspot connection off and then the next day it was on again... ***!!!