If I was served a summons, talked to the creditor and worked out a monthly payment. What form do I need to send back to the courts to show this?

If you and the creditor reached an agreement before going to court, the creditor needs to file a motion with the court to dismiss the case since they were the ones that filed the lawsuit. Contact them and make sure that they do this. Also, contact the court and find out if the court allows you to do it (I doubt it but courts have their own local rules and may allow it). Make sure that the case is dismissed before the time is up to answer the summon or else a default judgment may be entered against you. If you want to make extra sure, answer the summons (it's usually a form called an "Answer") within the legal time (usually 30 days after service) and appear in court. While in court, you can explain to the judge that an agreement was worked out between you and the creditor.   By the way, make sure that the agreement/payment plan is in writing. Or else the creditor could claim that it didn't agree to anything with you in court.