Insurance paid 80% and charged other 20% deductible unpaid. I have a judgment

I had a broken hand repaired by a doctor who was referred by a mutual friend, another doctor. He accepted my insurance which paid 80%. He never told me verbally I would be responsible for the other 20%, though I may have signed something to that effect with all the forms signed. He wanted over $2,000. Then he lowered the amount to about $1,800. i paid over $800 but started paying $20 a month because I couldn't keep up with the agreed payment plan. He sent it to a collection agency. The agency says I now owe about $2,600-$2,800. Since that time I moved out of state and found out on my credit report that thea gency has sent it to court in NJ. They don't know where I live so I guess that is why I have not been server a summons to appear. Do I have rights because I was paying? I never signed any agreement, it was verbal. I stopped paying when the collection agency contacted me. Or should I bargain? Seems I am getting the shaft!
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Any resonable person knows they have to pay the other 20%. You should have paid. No excuses.
When a creditor accpets a payment plan they cannot collect the full amount if one stops paying unless they go to court and you do not defend yourself. You didn't and now have a public record. This is a lawyer thing though. I am not sure what your legal rights are.
If you are being sued in court you need to find a lawyer anyway.
Are you being summoned to court?