Jet & RSC calling for payment - NO PAYMENT DUE!!!!

RCS keeps calling my father and says there is an outstanding balance on his Jet account even though the account was settled in full more than a 2 years ago. No amount of explaining will convince them otherwise not even proof from the debt review and I cannot understand why they keep calling him. He has went to 2 different Jet stores asking if it shows any outstanding amount but the people at the store says there is nothing outstanding. I can hear that the calls are making my father nervous so I will block it from his phone and get an attorney to get the Jet call centre agents to stop harassing my father and make sure this is posted on every social media page regarding RCS and Jet!