Water leak not fixed

We had a water leak on our geyser, we registered a claim and a plumber was sent to do repairs. They assessed the problem and replaced the geyser, since then our taps are spitting and blowing air, the plumber has been back 4 times, they supposedly replaced the thermostat and the pressure valve on the new geyser, installed a pipe sticking out of my roof, with no results.. Then the plumber said it must be that our taps that are faulty, so we replaced the taps in our bathroom and kitchen, same problem persist. Since then the same leak that we reported originally is back again. We are at our wits end, we phoned numerous times, sent emails to complaints, still no joy at getting this fixed!