Revenue Code Contract Rate

My insurance company gave me a lovely negative $3000 “member discount” on a single line of an Explanation of Benefits. 3 months of phone calls later I finally got someone who explained the revenue code is a “lump sum” billable code for all procedures, services and supplies performed/used during that revenue code and compared it to the cost of an “all you can eat buffet…even if you only eat a little bit you’re still charged the maximum amount.” The issue is I have another 10 pages of stuff that would likely be rolled into the procedure in question, but is shown as itemized charges that they seemingly wrote off/ignored. The total cost of all of the codes exceeds the contracted rate they’re telling me. How do I get my insurance company to actually reevaluate this claim? They keep telling me the EOB is correct with no additional explanation and stuff a bunch of contractual coverage rate (X% after deductible for type of facility not a specific procedure/charge code) paperwork at me.