SimonMed Imaging

I had an MRI on December 5, 2022 and paid $346.20 using my FSA prior to the scan on that date. About a month afterwards, I realized I was overcharged & they should have accepted what my insurance paid. I have spoken to them on multiple occasions since early January 2023 and still have NOT had the amount credited back to my FSA. The billing office isn't located at the Imaging Center, and I don't know who else to contact regarding this issue. Any help would be greatly appreciated.