Advice please just moved house and outstanding utility bill from previous occupier!!

[Dickorydockwhatthe]

We moved in Friday, received bill addressed to occupier with outstanding balance of £109 meaning they have blocked us from switching to our previous company that we had in our previous house until bill is settled.
The new house has actually been vacant for a month because the previous owners sold it to a building company as part of an exchange and we then brought it from the building company. We obviously took meter readings as soon as we moved in but unable to ring due to them not being opened the weekend. We had planned for the switch but our supplier was blocked so now they say we will have to also have a bill with them 🤬 any advice???

You will probably need to send them a copy of your tenancy agreement or proof of completion date. They should only bill you from the date you took legal responsibility for the property (even if this predates moving in).
Just send any letters addressed to the previous occupier/owner back to the sender marked Return to Sender.