Problem with a purchase shown on your statement: Credit card

I received a call that I had an outstanding medical debt. They said they had a lein against me so I paid $4900.00 on my comenity bank credit card. A few minutes later I realized I did not have any amount due because we were in the process of selling our house and had paid off all our debt. I called the cc company right away and said to not let the charge go thru it was a scam. They said they had to wait until the charge went through to cancel it. So we waited then we sterted getting past due notices from them saying we owed the amount. We got a stattemet from the medical company sayign we had no balance and sent to them. They said they would review it and let us know. In the meantime our cedit score went way down. We contacted them again and they said we had to pay it even though we had a letter from the medical company saying we owed nothing. We just gave up and paid it. They we not professional at all and gave us no reason why they were charging us when proof was given we did not owe that amount. That is a lot of money to have to shell out and I hope you can help.