cello, Hi. I used to be a collector. There are laws that even collections and creditors have to abide by, and sometimes, they just don't. I'm not a lawyer, but, for example, I think there's a law that says that when the original creditor turns an item over for collections to a third-party collections company, they have to notify you in writing and name that company. Some creditors don't do that step. In that case, you might be able to get that debt off your report, legally. Although you still owe the debt. The laws are complicated.
Here's a law firm that specializes in it. They seem to know what they are doing and their rates are reasonable. They have some good information there and you can check w/ the Better Business Bureau in their city and even the Attorney General's ofc in their state to see if anything has been reported on them, if you are concerned about being scammed. They also have information about copycat services and other companies that do scam consumers, so you will know what to look out for.
Good Luck! I have dealt with my own credit situation, on my own. It can be done. And, I have paid back all debts, too. And my credit score has jumped 140 points!
http://www.lexingtonlaw.com/credit-repair-services/