Bad service

I received my heater on the 3 of August after ithad gobe in for repairs on the ignition button now the heat gage switched the heater of when it was low. Today on the 9th August the heat gage switches itself off even when on high so what must happen now? Yho who can i talk to to get my money back because i cannot keep reassembling this heater and taking it back to the store. They fix one thing and another fails. One thousand five hundred rands is a lot of money to spend on a product which keeps failing when i need to use it.