PLEASE HELP ME REPLACE MY GEYSER

I have bought a geyser that was made by Heat Tech , I was told that the geyser has bust , my geyser has even finished 5 years, it was almost 2 years.

The geyser looks brand new from outside but it has rusted from inside and and it's leaking on all over, My plumber told me this is a factory he has been fixing gysers all his life but he has seen anything like , so this means they made the exterior to be solid , but the interior was useless.

They have a company here in Port Elizabeth that is their supplier, they told me they also stopped selling their geysers because clients are always coming back with problem so that is bad for their image.

This morning the have sent Pieter Rydemeyer Plumbers to come check the geyser out, they have told me they cannot replace the geyser, because of the warranty void. This is a ****