Blowing hot and cold air at intervals

I bought 4 appliances from Clicks which 2 of them were the Safeway heaters. The delivery was made on the 4th of August 2020 and i immediately tried them to see if the work. The 1 heater worked fine however the other was blowing hot and cold air at intervals while he thermostat is set to hot. It would make a sound s it would switch from hot to cold and vice versa. This is extremely disappointing as the product was bought to use for heating purposes and now it has to be returned again. We order things online so that we do not have to go anywhere during the Covid-19 pandemic but now we have to go to the store to exchange it this is not good service at all and i am very unhappy about this.