Paid less than market value for my bitcoin when selling through luno

I have been using Luno for many months and was actually very happy until yesterday when I sold 0.6302 bitcoin and should have received R41 000... however when the transaction went through I was paid just under R36 000 so was effectively conned out of Around R5000!!

I have sent four messages on the Luno help center and have screen shots of everything which clearly illustrates that I have been conned... I received some one line generic response and nothing since.

The rate that my bitcoin was converted at was less than market value and is much less than the lowest rate shown on lunos graph across the entire day letalone the time that my transaction was concluded..

I am still waiting for Luno to renfund me my bitcoin or pay me the balance of my rands... I will be withdrawing all my money from their account and cautioning everyone I know about Lunos MO when it comes to processing sell orders as this is a ****!!