你可以寫一個正式的letter給debt collection company within the date..

Don’t include any personal information. Just states that you don't own $2000 to that company. If it was me, I won't provide any details. Just have a record you formally reject that debt. In case they default as you lose. After that, I won't answer anything unless they sue you and go to court or they give you a settlement you want to accept.