First off, Portfolio is a junk debt collector and has to seek judgment in your state of residence. If this debt is older then 3 years, then it is "time barred" or also known as beyond your states statute of limitations to seek legal action. (see source)
Next check to see if the "summons" is real, it should show the court and the docket number. Call the court to verify it is authentic (Portfolio has been known to send phony documentation).
If the debt is time barred then that would be your defense and your reply to the summons.
If the debt is NOT time barred, then you need to contact the court and file a SWORN DENIAL. Most courts have a blank form you can use.
A sworn denial makes it harder for them to prove their case. The sworn denial needs to be typed, signed, notarized, filed with the clerk of the court, and a copy sent to the collection lawyer. It needs to be a graduated denial. In other words, it needs to say, "I deny that this is my debt and if it is my debt, I deny that it is still a valid debt and if it is a valid debt, I deny the amount sued for is the correct amount".
This eliminates the Sworn Affidavit of Account that the collection attorney has. Now they must produce a live witness to testify about the debt. The requirement of a live witness changes the dynamic of the collection action considerably. The witness must be from the original creditor and also provide original documentation. This increases the chance the action will go no further.
As to free legal help, you might qualify for legal aid depending upon your income and assets. Check you local legal aid office.
Hope this answer is of help to you
LEGAL DISCLAIMER: The answer provided here is intended for informational purposes only. It is not intended nor presumed to be legal counsel or professional legal advice
Hope this helps answer your question.