Terrible Service to customers

I bought a radio with sound louder September 2018, installation was done I think October 2019, the installation took two days because first day I have no idea what was confusing the technician, second day he came, spent a full day doing the installation. In October I noticed that this installation wasn't done correctly,

* GPS navigation doesn't work * When I reverse the music stops * When driving the volume goes up and down automatically without being touched. * When getting into the car it takes long to switch on, you need to constantly touch the screen. * By car info it says no signal, basically it doesn't sync to the car

I reported this to the technician Tebogo two weeks after installation and he said he would come sort it out, he said maybe there's something he could have incorrectly done with the wiring.

Followed up with him, still nothing, November 2018 decided to send an email to their workplace instead of communicating directly with the technician, emails have been going back and forth and still I haven't been assisted, they told me that I didn't pay R400 for my start button and I informed them as soon as they fix my issue which I paid R15 000 for, I will pay their R400, it's 30 June 2019, I am still waiting for a date and technician......

Service provider never looks out for their customers, to think I even referred people to this company, anyone please advise on this platform what steps I need to take?