Delonghi Gas heater - defective after 1st switch on- wait 21days before feedback

I bought a Delonghi heater two weeks ago only to find its defective, doesn't switch on and when I took it back to shop - firstly the service was terrible, waiting over 30 minutes to receive any kind of service. Clearly stuff either don't know their policies when someone returns goods or just slow. - The really ridiculous part is its winter and they tell me I have to wait 21 working days before I receive any feedback on the heater. So for 21 days of this winter I'm just meant to make do without a heater even though I've already paid for one. - Really terrible service, will never buy electronics from them ever - imagine being told oh we need to check your fridge for 21 days in the interim just make do without.?