Poor work etiquette and half a job done with no certificate

Morne Du Plessis installed our inverter and battery in May 2023. His men came out to do the job which he never checked. The next day we discovered the other part of the house was not connected and had no power during loadshedding. His guys came out again and this was sorted. Then we discovered 2 months later that the guestroom and en suite that we don't often use was also not connected. We were unable to get Morne to come out to add this onto the battery and inverter even though we had paid him to place the entire house onto this. He eventually referred me to his cousin to finish the job. Etienne Du Plessis came out to do an assessment and quoted me a ridiculous amount of money stating that there were many things wrong with the DB board. I once again reverted to Morne as I was not going to pay out any more money since his guys were the last to work on the board. I tried for many months to get him to come out to finish the job, but also to issue me with a compliance certificate for the work done on the DB board to install the battery and inverter. When I threatened to report him, he turned very nasty and claimed to not owe me any certificate and that he had to had to keep coming back (for work he had not completed I might add). I am absolutely disgusted by the work etiquette, the manner in which I was treated and the shoddy piecemeal manner of work done. Do not use him, stay clear away.