Debt collection — National Credit Systems,Inc. (GA)

Debt is not yours. National Credit Systems , Inc is clearly reporting incorrect information. I do not owe XXXX of XXXX XXXX XXXX. I wrote them a letter asking them for physical proof this debt belongs to me. 30 days letter, they send me back a letter saying I need to prove it is not my debt. That is illegal. They are a total scam and they are ruining my credit.