I have some bills in collection and due to my work schedule I am unable to go into there office and pay them, so my sister take the cash in full into them and they refused her payment she was not asking for any information on me just wanting to pay the bill, now I have been served with judgement papers after they refused the payment in full is there any laws on this.

File notice of intend to defend with the court, than you can ask why they refused payment in full in front of the judge.