Product: Debt collection

My wife incurred a medical bill from XXXX Specialists, for which XXXX Specialists  never sent any billing out for, nor did they attempt to contact us to let us know there was an amount owing. Our first notification that there was any amount due was when we received the collections notice from Express Recovery Services.

Attempting to pay XXXX  online through their portal, they want to charge a " convenience fee '' for paying online. So I figured that talking to a representative they would be able to waive that fee. 
In conversation with their representative and explaining the situation, I noted that we never received any billing from XXXX  Specialists but that I just wanted to be done with this and move on. They also attempted to make me arrange payments for my step child 's bill as well, even though that billing is supposed to be paid by their father whom XXXX Specialists has information on. 
They added on other collections accounts they stated were in my wife 's name and wanted me to pay on those as well, to which I replied that I knew nothing about them, that they weren't my responsibility, and that even if they were able to provide any information about them they were likely too old to be collected on. 
There was some discussion from their representative about a deadline to pay before they reported it on my credit that would cause damage to my credit score. I told them I just wanted to pay and requested we move forward with the payment. 
As I was about to make payment, they also asked other information about me that I was not comfortable sharing, nor was it any of their business. I told them as much and requested that we move forward with payment. As they stated a final amount, they wanted to tack on a " convenience fee '' again, to which I stated that they were not entitled to it, that their " convenience fee '' was illegal, and that by attempting to charge more than the actual collection amount they were breaking the law. They asked for my checking information, to which I replied " I will not provide that information to you, you can accept my proffered payment method or state your refusal to accept my payment '' They again stated that I needed to make the payment, plus the " convenience fee '' or they would report this negatively to my credit. 
I hung up the phone. They have my number, they can call me back if they care to discuss further. 
Because I didn't want my credit damaged as they threatened to do, I went to their website later and made the payment. Their payment website has a " print '' button, it does not provide receipts that are printable. They come out blank. I ended up screen capturing the receipt so I would have proof of payment beyond my credit card receipt. ( screen capture of payment receipt attached states " cancelling '' as their website locked up while trying to print and then would not cancel the printing either ) This company discussed the debts of other people with me and attempted to collect more money than the debt that was owed. They attempted to bully and harass me into paying the debts of other people, and threatened to post negative marks on my credit report if I didn't comply with their demands immediately.