Spark Energy

I lived in a block of flats, I lived on flat 4 for 2 years and July 2017 I moved out, few months after my Neighbour called me saying there is letters in my name as all letters come on the main door outside so she send me photos, I was shocked to see spark energy is asking me for around £1500 to pay for flat 1 which I never lived on! I call them and asked them who told you i am responsible to pay the bills on this address, they said no one but we got your information from a credit agency and we where told that you live there!!!!!!!!!!!!!!!!!! So they saying I have to send them proof that I lived somewhere else!!!!!!! I thought the accuser has to proof you are wrong not the accused to proof he’s innocent!!!! I can’t explain how badly angry I am! Sorry about my spelling my English is my 2nd language