If a creditor contacts you after you have filed your bankruptcy case you can bring a motion for sanctions against them. You can collect actual damages and attorney fees. If doesn't take much. A simple phone call can be enough to to violate the automatic stay. The amount of damages varies. I have gotten as little as $200 plus attorney fees to as much as $1200 for a stay violation. It depends on the extent of the violation.
However, it is worth noting that the Bankruptcy Code allows for punitive damages if the court finds the creditor acted egregiously and with malice.
The point is Bill Collectors must cease all collection activity once you have filed. That is what bankruptcy protection is.