Lawson Family Dentistry Did not follow Insurance Guidelines Urbandale Iowa

I am an Active Duty Service member that received a routine cleaning from the Dental Office back in January.  I received a treatment plan that would resolve all the issues/cavities that were needing attention.  I explained to the Dental Office how my insurance worked and that I would need a pre-auth for the treatment plan and that it was needed to be sent in by them.  They scheduled me for several treatments over the course of a period of time.  During each visit I was told payments were due for the treatment.  I called my insurance company every time I was in the office and was told that no payments were needed to be made and that the pre-auth covered the visits.  On my final visit I was told that the insurance company was not covering parts of the treatment.  At that time I called the insurance company, once again in the office, and they explained to me that the Dental Office was performing treaments outside of the guidelines of the insurance company and that it is not my responsibility nor the responsibility of the insurance company to pay on these treatments if the Dental Office failed to follow the guidelines authorized by the pre-auth. I explained that to the Dental Office and they said they were going to try and resubmit a rebuttal. 

Today I received a letter from the Dental Office saying that I should have been aware of the treatments being performed and what was covered.  I never received the pre-auth from the insurance company, it goes strait to the Dental Office.  I was also not explained that the Dentist was going to perform treatment outside of the pre-auth.  What they were doing was trying to pull one over on the insurance company to collect more money!  They sent a very threatening letter stating I signed a form consenting to pay uncovered costs (TRUE) but not uncovered costs for unknown treatment rendered outside the insurance companies pre-auth.  She has threatend to send the $861 bill to collection or her lawyer.  (being a person with a 745 credit score I am VERY displeased).  They have since dropped supporting military insurance, which is a disgrace because all would be fine if they followed the guidelines of the insurance company.  I would recommend being aware of the scams they are trying to pull on the insurance companies, and the lack of care and respect for their patients!