Gunbroker.com G B Holdings Over charged and received NO customer service and NO phone Number to call, Internet

Discovered a error on a billing invoice.  Gunbroker had charged me twice to list the same item.  It was only a small amount = $3.20.  But I had sold over 30 guns over the past 90 days through their website.  I had paid over $1000 in fees to them during that same period.  I brought the issue to their attention and got the cold shoulder.  I sent 6 emails between Nov. 25 and Dec. 16, 2010.  Only one was responded to and they did nothing (offered no solution).  I have repeatedly asked to have someone call me from Gunbroker customer service, and have not called.  No phone numbers exist on their website, and customer service is via email only (hard to access too).  My small issue turned into a big one because they never took the time to resolve my $3.20 credit request.  After sending them an email today stating I was going to request a charge back from Visa, they finally responded.  Not to my issue, but to threaten me with a $50 fine for any chargebacks made.  This company signifies all that is wrong with big business and our country. Morally and ethically bankrupt!