Did I get scammed?

I got a spam call on 6/12 for from a collection agency to collect on a medical debt. Their initial offer was significantly less than the debt owed ($63 to the original debt of $560). I paid it without asking too many questions. I did ask multiple times if they were sure that was all I owed and they assured me the account would be closed after making my payment.

I got an email 4 days later from a larger collection agency (ameri collect) claiming they owned the debt. I called them and got it down to $300. I have not paid it yet but they said they would honor it for 2 weeks.

I called the the original agency back that I had paid on the 12th to verify everything and asked if maybe the debt had been split up somehow? They assured me that the debt was all paid and that ameri collect must have a different debt?

Im so confused and don't know what my next step should be. I want to get it resolved ASAP.