I'm paying off old debt, what actions do I need to take to make sure that the collection agency I am paying is actually the current holder of the debt?

I don't what to find out 7 years from now when it's ready to fall off that the debt was sold prior to the acency collection I'm in contact with taking a payment or selling it after the fact. What actions can I do to make the collector submit the debt as paid to all credit reports and ends the debt?