After-market support non-existent!

Solar Guru did the conversion of my existing geyser to a 20-tube solar collector early in 2023. I now have some issues with the installation, which I want them to investigate (I accept that I will need to pay for this call-out service outside the warranty period); I sent them two emails already last week (three different email addresses were copied in the request), and no one has even bothered to respond to any of my requests.