Gold Key Credit Rude,uncooperative, and dense brooksville, Florida

This started with a 2/16/10 dr visit, at which time my wife paid a $25 co pay. We did not know our insurance co treated clinics like an ER so the copay should have been $50. The clinic never sent us a bill for the other $25,they just turned it over to Gold Key on 10/8/2010. We first heard from them on 12/10/2010. After i talked to the clinic and my insurance co, both of which could have said something, it was obvious we owed $25 more. I contacted gold Key, and said I would remit to the clinic, they said ok. I sent a check on 12/30/10 to the clinic which cleared on 1/4/2011. Since then I keep getting threat letters, 2 so far this month. I call them to no avail. They asked for a cory of the cancelled check. I got one from the bank and sent it to them. I keep telling them to call the clinic, i owe nothing. I dont know what else to do. $25 is not a problem for us to pay, but if I send another check now to gold key, after all this there is no reason for me to believe they wont continue the harrassment. My wife works in the state attorneys office, and we cannot have people reporting credit problems. My attempts to talk to the clinic are also futile. I get a blank stare and they say that is all handled by another company. Ony gold key knows who they corresponded with.