Failure to deliver goods or keep in touch

We had a gas geyser installed over a year ago. we can't shower cause it doesn't work properly, the kitchen doesn't get hot water instantly. we have paid for the job but the job is incomplete. No cage was installed, no certificate of compliance has been provided. Every time we call, he makes empty promises or hangs up on our calls. Its been a year and still no progress on getting the issue resolved.