How Do I Get Written Approval?

I have United Healthcare.  They approved my surgery on November 21 and, supposedly, mailed approval letters to the surgeon, the hospital, and me.  None of us have received the letter.  On December 6 I requested another letter be mailed to me.  According to UHC, I have to wait 10 business days to receive it.  My surgeon's office has requested the letter be faxed to them.  No fax received.  I requested the letter be faxed to my surgeon.  Again, no fax. My surgeon's office is closing December 22 for the holidays and won't be open again until January 2.  I really wanted to have my surgery date scheduled before this year was over because I want the surgery in January.. Is there anything I can do to light a fire under UHC?  Thanks.