Signet Financial Group FAILED to honor my service contract refund agreement. I was told check was in the mail ,but no check ever came! Vacaville, California

   I bought a Ford f250 in Sept. 2004 with an extended warranty through  Signet Financial Group. On Sept.2010 (exactly 6 yrs.) I contacted Signet, they sent me the paperwork needed to get a refund. I overnighted all the papers and the pictures they asked for back to them. After a few weeks I called them and finally got to  talk to some one. They told me I was approved for the refund and to call back in a few weeks. I called them back in a few weeks and they kept telling me to call back that they were processing my refund. This went on for months.
  In January I called and they told me that a check for $1865.00 was being sent out to me and that I would get it on or around March 11,2011. The Check NEVER CAME!!!
  Now I cannot even get a hold of them. Who can I talk to on this? Signet gave me a runaround and They RIPPED ME OFF!!!!