$9000 insurance not cover

I'm an F1 and buying student insurance for a couple of years. last august, bought a new insurance. I had a D&C surgery (not for abortion purpose)in May this year. The total cost is over $9000. My insurance won't cover a penny by saying that it's an pre-existing condition, which is not true. I had never seen a doctor here in the U.S before this time and doesn't know anything about the procesures. I asked the doctor before the surgery deisicion was made. He told me that my insurance would cover. When the bill came last night, I was astonished. Anybody could shed some light on this? Can I sue the insurance company? or could I negociate the price with the doctor? Waiting online for your kindly help.Thanks.