United HealthCare Services review: billing department

On November 28th 2014, following the consultation of three separate specialists, my son had an urgent CAT scan. After 10 months, UHC have yet to settle the bill. When UHC fails to pay a bill, the service provider turns to the patient for settlement. Due to an autism spectrum disorder, my son is on Medicaid, which I am informed, should have prevented me from being invoiced directly. Nevertheless, every month I am the pinball between UHC and the hospital that provided the scan. I have made numerous phone calls to both parties, trying to bring this issue to a close. I have done my level best, even though I don’t feel it is my place to resolve a billing dispute between the two parties. The hospital has run out of patience and has put me into debt collection measures. Here in summary are the excuses provided by UHC for failing to pay: Not our patient - 
Laughably easy to disprove this one Payment automatically rejected - 
 Why? Because it has already been rejected once Patient has other insurance coverage
 - so wish this were true; dealing with any other insurance company would have been a blessing Wrong hospital
 - I was there with my son, I know which hospital we were in Payment already made
 - Apparently a payment was made on February 20th. This was before the 
hospital was asked to resubmit the claim in March! This particular piece of erroneous information caused much annoyance, as I was put in the position of perpetuating a lie.
Tellingly, I continued to be billed. Service not covered
 - An urgent CAT scan deemed necessary by three separate consultants is not covered? 
And why did it take 10 months to come up with this excuse? Each time a correction is made, it takes an entire billing cycle to come into effect, allowing for yet more miscommunication and vexation. To further add to my frustration, I have to pass a menu system every time I call, and speak to a different operator each time. I have specifically requested that one person take ownership of this long running issue, but that has yet to happen. Nor do I have a direct number to call, and nor does anyone reach out to me. On many occasions I have requested call backs, to no avail. Last month I took a day off work to try finally to resolve this matter. I was assured that UHC would send a “Cease to Bill” notice to the hospital to halt debt collection measures. I provided the operator with a fax number, email address and reference number so that UHC could efficiently get this message sent to the hospital billing department without delay. However, I was told that an expedited letter is all that could be arranged. I insisted that a copy of this letter also be sent to me. A week later, no letter. I called again, and was told that it is not policy to send expedited letters - so a direct contradiction to my previous call. Regardless, it seems as though the operator of the day will merely add an instruction to my account log, and assume their role is finished. There is clearly a breakdown in the anticipated chain of events, yet with no one claiming ownership or overseeing the process, it is the customer that is being left vulnerable. At my last phone call, I asked about the complaints procedure. I was assured that someone would call me back. Another week has passed ... still waiting for that call, still waiting for that letter.