A credit repair company initiates credit challenges to bureaus when they notice errors in your credit reports. Credit report disputes involve challenging credit bureaus, drafting goodwill letters to remove late payments and contacting data furnishers to verify old debts. Credit repair specialists review the results and, if necessary, escalate the dispute process.
Here’s a good example of when a reputable credit repair service can help you do something you may not be able to accomplish yourself. If you have a collection account that’s been sold to a few different debt collectors, it can appear on your credit report multiple times. That information is accurate but having that one debt dinging your credit score multiple times doesn't meet the “fair” standard that Padawer mentioned.
Reducing your balances on credit cards and other revolving credit accounts is likely the better option to improve your credit utilization rate, and, subsequently, your credit scores. Consistently making on-time payments against your debt will also help you build a positive credit history, which can have additional benefits for your credit history and, by extension, your credit scores, too.