GunBroker.com Gun BrokerGunBroker.com LLC Charged me for a transaction that did not complete. Sent me a letter stating they are sending me to collections. Kennesaw Georgia

I listed a pistol on gunbroker.com and realized the listing was incorrect.  As I was about to change it a buyer used the buy it now button.  I contacted the buyer and told him about the mistake and he chose to not buy the gun.  Even though the transaction never went through I am now being told I owe the fee for selling the gun.  I cant get ahold of the buyer so they are insisting I pay it or get sent to collections. 

Customer service is rude and will not give out a physical address to the company or give me their phone #.  I would like to settle this in court since I live neer the city they claim to be in but I have no physical address to serve.  The amount is under a $100 but the principal of this is worth a lot more to me.  I dont like to be threatened or bullied by people and if it costs me money to push back I will pay it.  My next step is reporting them to the BBB.