Hello, I Had A Colonoscopy And Had No Polyps. I

Hello, I had a colonoscopy and had no polyps. I has polyps three years ago and five years before that. Even though I had no polyps and the doctor told me I don't need another colonoscopy for ten years. I was billed $4,000.00 and after the deductible I owe $2,400.00. If the doctor didn't have to remove anything why was in not covered? I can't afford this. Thank you