Why would it say "to the occupier"? That makes no sense.
This happens. I rent out a house. Names of tenants and my names are known. After the last but one tenant moved out, I had a month unoccupied, all the utilities companies where informed, including that it was a rental property, and that I was the owner, and that my correspondence address was my actual address.
They sent bills to the rental house, addressed to the occupier (from Spark).
I thought it was a scam! (because as I said, they had all the names and contact details available to them)
Turns out it wasn't (well, not exactly - in that there was some outstanding amount, but it wasn't the amount on the bill, which was not labelled an estimate, but turned out to be an estimate).
We went through the ombudsman, the lot, pointing out how underhanded it all was to act this way - the bill was quashed (it wasn't 500, it was a lot less)
Do ring the company - do confirm readings, do tell them that this is not your account and that you are the new owner and you are not responsible for this bill. Do expect a fight.