Product: Debt collection

I owed {$4500.00} in XXXX bills. I was told by their legal representative ( XXXX ) that I needed to pay it in full. I did not have that much money and a garnishment would put a huge financial strain on my family, because we would not be able to pay current living expenses. 
XXXX told me that I could enroll in a payment plan. The only thing with that is that they would have to take legal action and so I would owe more fees. The total would be {$6900.00}, but I would not have to pay it all at that time. So my choice was to pay {$4500.00} today or {$6900.00} over a longer period. Why did she need to take legal action in order to accept payments from me? I did n't want to question her because I was scared that she would pull the deal and I would be expected to pay {$4500.00} immediately, which I did n't have. 
I have been making payments on time, in fact I have made XXXX consecutive payments. By my calculations I have paid {$3300.00} on this bill. If it was only {$4500.00} like it had been, it would almost be paid off. However since they embellished the amount to {$6900.00}, I still owe almost half of the debt. 
In XXXX my debit card number was compromised and someone made some fraudulent charges with it. I called the bank and they cancelled the card. However I had forgotten that this debt collector was attached to the card. Since they always deduct the funds automatically, I never think about it. But when I balance my checkbook at the end of the month, I compare all of my online charges. So when I was looking at my budget for XXXX, I saw the charge that was supposed to have gone to this debt collector and I noticed that it was never deducted from the bank. I immediately called them and spoke to XXXX. She said that they had tried to reach me by phone during the month. They never left any voice mails and my call log on my phone does n't have any missed calls from them. But XXXX said that the bill is due in full. I told her that I could n't do it, and I explained to her what happened in XXXX and I told her that I was calling them on my own to give them my new debit card number because I just discovered the mistake. She did n't care about anything that I had to say. She would n't take payment or my new card number. 
She said that I should have alerted them the moment that my car number changed, and although I agree with that, I would have if I remembered that they were using my debit card. Some bills just deduct from my checking account so I do n't need to give them my debit card. 
Since she is demanding full payment, I would like to know if adding on those extra fees in the beginning were legal. When we were talking about a payment plan, the bill was nearly {$2400.00} smaller. She did n't have to take legal action as part of our payment arrangement. She could have allowed me to begin making payments on the current bill with the appropriate interest. I did n't have all the money so she knew that they could get more over the long run. 
XXXX told me this week that they offered the payment plan as a courtesy. But since I paid nearly {$2400.00} for it, I do n't think that it was a courtesy. 
Since XXXX would not allow me to make a payment on my bill, I went online and did it there to show good faith that I want to get it paid off.