If you did not include this debt in your bankruptcy, then it was not discharged, and you may still owe it.  However, the apartment manager's assurances that you did not owe anything may be used in your defense of the debt.  If they get a judgment against you, and you still do not pay, they will be able to garnish your wages.  Prior to this going to trial, there should be a pretrial conference offering an opportunity to settle the debt.  Settlement for a lesser amount is probably your best option.