KIA Motors Hatfield, Doesn't pay suppliers

I'm a service provider based in Pretoria and my company name is Oceanside Holdings Pty (Ltd). I was given a job to wash the windows at the dealership on the 12th of March 2018 which of I did and I later submitted an invoice and I was later told to re-submit the invoice as they had lost my invoice. Since then I have been sent from pilar to post, I have made countless phone calls but I'm always told they a busy they will get back to me but they never do. I have sent emails to the dealer principal Mercia Kroucamp and she has ignored my emails and didn't even bother the reply my emails.