Rudolph Inc

I checked my credit report recently because I received an alert that I missed a payment. I logged onto my account and it was from Rudolph Incorporated. My car was repossessed in 2016 and since then Rudolph has sold my account to a creditor Pacific Credit Exchange. I cannot pay two different people for the same item. I called Rudolph and first they were very rude. The manager I spoke to told me that my account is still active and collecting interest and it will never close. I said but you sold it and that creditor is on my credit report, I am not paying you both. She just kept saying they weren't going to correct their incorrect vindictive action. The reason I say vindictive is because this is a very small office. I believe they only have one office, maybe two. This company only has two offices so the information is easily attainable if there are only one or two managers handling these accounts. Needless to say I had to file 3 different disputes because Rudolph wouldn't budge. The rules are the rules and the laws are the laws. I cannot and will not pay two different people for the same account. I asked them to close the account and bring the balance to zero since it was sold and again, I was told no. I am not asking to remove the item from my report, what I am asking is that the balance be brought to zero as the creditor has already paid them for the account. I don’t understand how they expect it is legal and okay to want to be paid twice for the same account. This practice is unethical.