In my case I finally reached out to the city councilman's office for the district I work in (I lived in Henrico) and he put my in contact with the mayor's office. I ended up exchanging emails with what appeared to be some fairly high up folks and then the head of DPU herself. And that's when it finally got resolved. Had it not been I was about to go to the news media and had I found it sooner I also would have filed a complaint with the SCC:

https://scc.virginia.gov/pages/Utility-Complaints

Might be something to consider in your case.

By comparison, when I called Henrico DPU to close out my trash/water/sewer I made one phone call. They sent me a final bill, I paid said final bill, and never heard another word from them.