I received a debt summons, called the attorney representing the plaintiff and settled for a lump sum. Do I still answer the summons?

A summons must be answered regardless of what you and the creditor agreed privately.  It is a matter of procedure, and if there is nothing in writing then some unscrupulous creditors might attempt to get a default judgment against you.  An alternative would be to file a motion to dismiss instead, which would be based on the agreement to settle.  In the end, however, the easiest route is always cooperation, and it may simply take a call or letter to the creditor asking them to voluntarily dismiss. This answer should not be taken as legal advice, which would require familiarity with all of the facts of your case.  If you need further assistance, you should consult a qualified attorney.