How can I defend against getting sued by a third party debt collector?
We cannot give legal advice, and are not forming an attorney-client relationship with you. The following is not a substitute for the advice of a local attorney. But we hope the information will be useful.
If you owe the money, it is difficult to defend, other than by declaring bankruptcy - but that is a drastic step. In that case you would want to consult a local bankruptcy lawyer.
If you claim you do not owe the money, or do not owe all of it, you can go to court and make the creditor prove that you owe it. It would be most preferable to be represented by a lawyer in this effort.
You could probably work out a payment plan with the creditor if you are able to contact them. You may be surprised what sort of deal you can work out. You may want to tell them, you cannot pay all, but you can pay X, at x per month. And see if they will agree to a complete settlement of the outstanding debt based on that arrangement.
In any case, to protect your rights most fully, you should retain the services of a local attorney.