I did have debts 3 years ago to state debt recover...

I did have debts 3 years ago to state debt recovery ive paid it off. Now this company is trying to tell me I haven't paid and it's been passed on to them.
I called them up on multiple occasions they have said I owe them money being different amounts. One lady said I own $1,400 and a man said I owe $800.
They are seriously a joke