It sounds like you should be contacting the court that issued you the summons. But, I would first call the company that is demanding payment, with a witness for you on another phone line and inform the company that someone else is on the line as a witness. See if you can negotiate some sort of payment plan. I did this very thing recently. It worked. I have a payment plan I can afford. The person that I had on the other phone is a friend who is a CPA. But, I know that this type of negotiating may not work with every company as I tried it with another, and it didn't work.
If the company will not negotiate with you and they say that you should be directing your inquires/communications to a court, then I would find yourself an attorney.
For information concerning Statute of Limitations concerning debts owed, information that you find on the following site may be of help to you. I hope that it is.
Statute Of Limitations For Debts