What do you do when advisors just don't reply?

Through the ombudsman OVO said it was going to use an estimated reading. Asked me to say whether I was ok with that which obviously i was given the actual reading belonged to the previous tenant. They gave me an estimated reading that was higher than my average use, even though I provided evidence that I wasnt even in the flat half the month. Disgraceful. And now because the Ombudsman have technically done their part, and a resolution, albeit a iseless one, has been achieved, Ovo refuse to deal with me because I accepted an offer that didnt even show the final bill. Cretins.