I have received a bill for $452. for a medical sur...

I have received a bill for $452. for a medical surgery. I have contacted them to let them know that I have insurance and I should not have gotten a bill. It has hit my credit report, because I should not have received this bill and never paid it. I need this removed from my credit report, but now when I call no one is answering. I need this balance removed from my report as my insurance has already paid it.