Capital one collections - is it a law firm or collection agency?

I posted back in 2006 that this Law Firm/Collection Agency sued me for my Capital One account which had fell into collection earlier that year. After going thru one collection agency it ended up at one in my state which was also a law firm. They ended up suing me for the amount due on the account. The problem I had was we settled out of court and on the paper which showed we agreed on an amount showed that I had a balance of around $570 then also sued for interest for up to Jan. of 2007 (which was the month the Court date was) which came up to $130 (not sure exactly how they came up with this amount) and $0 for court cost. Later I looked up the case on the Court site for my local court system and seen there was a $50 court cost added which made it around $700. I was fine with that since I was paying $50/month from Dec. 2006 thru Dec. 2007 which should have me have $94 left but on the statement they sent to me it said $131 which seemed odd to me I asked them were they adding interest or something and they said they weren't it was just the amount remaining but the math wasn't adding up. I paid the $131 anyway and at least for now, it should be paid off, which leaves me 3 collection agency left to deal with at around $150 a month for all 3 ($50/month each) But one thing I am finding it strange one of my CA is collection for an account which one of my other CA is listed as originally collecting and the one its collecting for is a Citibank Visa, which I don't really recall having, later in the year I am going to get my free credit report and check exactly when this account was open. I used to have 2 Assoicates Visa account both went to collection one I paid of in 2006 and the other now Midland Credit Mangment is collecting, but ERC is collection the Citibank for MCM, and I could have sore that one of my old cc account which was closed in 2001 was sold to Citibank but at the moment not sure, and I can't find my credit report i printed out last year.