Installations not according to industry standards and BAD service

After a very long struggle to get the people to install a new Geyser after Discovery has appointed them we are selling our house.

An inspection was done and the installation that was done was not done to industry standards.

Calling the service center on Thursday 6th of Sept morning 10 am till today no one called me back.

Decided to call again today 10th of Sept at 10 am and spoke to a Lesego and i have forwarded the documents she required and when calling back she is not available as the phones are not working and then it came out that she was on lunch.

This is terrible service for people that did not do their installations according to industry standards.

What should be done for these people that is useless to come and correct their work.