Can a company send a bill to a collection agency without giving the person a chance to pay it

I work for a company last year and i quit them in oct. i just received a bill from a collection agency, stating that i owe them money. I never received a bill from this company. I called the company and they said that they never sent me a bill, That they sent the bill directly to the collection agency. I asked them why they never sent me a bill. They say that it is there policy to never send a bill to the person that they send it directly to the collection agency Can they do that and is that legal.