Non Payment of Account

We did pest control services for the owner, Chris of several Superspar or Spar shops in Montana and around Pretoria for 2 years, invoiced them again in October and beginning November 2017 for services rendered, to date (27 January 1018) still not received payment, only reason for non-payment we receive is that the owner must sign off. Had to cancel the contract as we were not paid for some of the services since July - September 2017. Second in charge Yanni, only involved for last couple of months, is very rude and verbally attacked us and falsely accused us of poor service delivery and mentioned that he wants his friend to do the pest control. He refuses to sign the invoices and to have the owner Chris sign off.