NON PAYMENT OF ACCOUNT

My company A.C.U.S.A ( Pty) Ltd did work for Mr Pienaars company at Rouxville School in Kuilsriver in June 2015 .On completion of the work an invoice was issued and that's when the drama started. Mr Pienaar assured me that the school had paid him in full and that he would forward me the payment well after endless amount of phone call( where he talks and talks and talks)and e-mails nothing has happened despite Mr Pienaar himself making idle promise after promise after promise. He has a bad habit of NON - PAYMENT something that the industry as a whole does not need. Am I being unreasonable here in asking for what is mine I don't think so all I ask is that payment be done and rest assured I will no longer be doing work for CCTV & Time Management