Not delivering the speed but taking the money

For the last 2 months I have been paying for a FTTH 1gpbs down 500mbps up. Despite numerous WhatsApp chats with SuperSonic (that take 2-4 hours to even respond to first message) regarding the connection speed and billing of R900pm. The max speed 340-440mbps down and 30-40mbps up. The standard request and question every time from support is: Send screenshot of speed test on 3 the different websites. Asking am I using wired connection Is there only 1 device connected When asking for a credit note I was told not possible. I am now going into my 3rd month with Supersonic with still no improvement since day 1.