Possible payment arraignment mistake? What now?

Hi, (Sorry this is so long)
I received a call yesterday while I was at work. This guy asks for the HR Dept and I told him he would have to call a different number because they were located in a completely different building. He stated that he needed someone at this number and I told him there wasn't an HR Dept at this number. He stated that he needed to speak with the HRD about delivering legal information for an employee. He goes on to say that the employee is Jennifer **** and he needs to deliver a summons for her. He gave me a phone number and a case number and stated that they're with URG. The person that he asked for is me. So I hang up and call back on my cell to check and see if it's a real company, but hang up. I call back and give this guy my case number and he says he directing my call. So a guy picks up and he sounds exactly like the guy calling asking for the HR Dept. So I ask him what's the problem, he starts in on you're being sued and just kept going on.....I keep interrupting saying why....he finally states, you're being sued for like $6,500. I ask what for, he states for your Clout credit card that you had. Ok, I had a clout credit card, it was in collections but it was nowhere near $6,000. My credit limit was $800 and the last time that someone tried to collect it was around $1500-2000, that I remembered. He starts stating that with attorney fees and all these other fees, it's now $6500. I'm pretty much saying yeah right, that's impossible. So, I'm at work and the phone rings and I ask him to hold on. I don't stay on the phone longer than a minute and he hangs up. This was one of the things that threw me off; he didn't seem to care, so I was like they must mean serious business. I've researched before and I've had another collection company come with the fake I'm sending you a summons tidbit but it never happened. So I call back and he's like I can be on hold for 3 minutes I'm busy. So he goes back to everything that's going to happen. He states that they're so aggressive because they're not a collection agency. He states that they sent me correspondence about the $6,500 dollars over 30 days ago. I ask when, he states it was about 6weeks ago in March. I ask if he has the right address, he reads me my address. I didn't receive anything. He states there are 4 ways to go about getting their money....wage garnishment, check my property and put a lien on it, possibly taking my vehicle if I own one, running my social and locking up checking acct....and I forgot the 4th one. By this time I felt really defeated. He starts talking nicer and states ok, maybe you didn't get the letter and on that letter we offered you a settlement of the $6500, 50% off. I could maybe offer you close to that today. How much could you offer? I really didn't want to offer anything because I wanted to research some more, but he states that it has to be something today. I read a while back that once you make a payment, it gives them a right to open the acct. back up as basically new again but I felt like I was out of options. I told him I could do a $1,000 by the end of the month. He stated again that he needs something today, what I can give. I say $200. He states when could I have the rest of the $3000, I tell him I could do $250 every two weeks after the $1000. So I gave hime $200 and set up an $800 payment for the 30th and the rest of the payments have been set up as well. Once he finished calculating, he states it's actually $3947. I'm basically in tears because I was scared, that I would be going to court or checking becoming garneshed, because I have a 4 month old. So he states he's going to send a contract with these amounts to my email. I get the contract and it states the original loan amount as $4,693.47. So I start thinking more...with a clear mind. How can he send me a settlement letter 6 weeks ago for $6,500.....it shouldn't have even been $6,500, because according to him, it's $6,500 because of attorney fees and everything else. They shouldn't been suing already if they were just making contact with me. So after all of this went down....I decided to pull my credit reports....I had already gotten my free ones earlier this year, so I paid for them. The debt doesn't even show up on two of them anymore and on the other it's scheduled to come off this month as well. The one report that it showed up on was Experian...they were the only ones that have my current job listed....and they were the only one that has a request for credit inquiry from United Recovery Group. The past due for my clout card was $752...No High Balance listed...and $800 as the limit. I remembered that I had an old credit report from 2010, also from Experian...and the High Balance is listed at $2,346. So after saying all of this, can anything be done now? The high balance is smaller than they're supposed orginial amount on the account. Is it too late to send a debt validation letter? Am I now responsible for this $3947 because I've set up arraigments on it? And are they going to put it on my credit report if I refuse to pay this much? I should've known better than this. I've read so much...but I just felt so weak yesterday. What do I need to do now? I want to cancel my debit card because they have my number but I don't want this to go back on my credit report and it's just about to leave. Thanks in advance!!!!