When you pay off debt collectors you might assume that the debts will be reported as paid in full and be reported to the credit bureau as the debt being paid off.
But most debt collectors are only interested in getting there money and don't always report to the credit bureau's that your debt to them has been paid.
Usually when your debt goes to a debt collector and they put a mark on your credit report you'll need to hire a credit repair agency and a lawyer to get your credit score repaired even if the debt has been paid.
If you don't hire a credit repair agency or lawyer to get the credit score fixed then it can take 7 years for the debt to be removed from your credit report and for your credit score to improve.