Insurance says I will owe $5K for bisalp

Be kind, I swear I’m not an idiot—I posted this question under the health insurance subreddit and people rudely tore me apart. I have an ACA complaint plan via Allied Benefits System through my employer. I’m not saying I was expecting the procedure to be completely free but $5K was a shock. I thought ACA covered most permanent birth control options? I have my pre-op appointment tomorrow, what questions should I be asking? I tried calling Allied Benefits System but was on hold for entirely too long and opted for them to call me back, I hope they will or I will try again. I just know having contacted them in the past, they are less than helpful.