Pest Magic that can't repel even a mosquito!

I purchased a Pest Magic pest repeller at Homemark Fourways on the 23/09/2019. I followed instruction to keep the devices plugged in all the time, however after more than a month my problem is still unresolved. When I try to return the product I'm told about their refund policy which in this instance is not applicable. The manual states that you can return your device with 14 days and at the same time the manual states that you should use the product for at least 2-4 weeks, then your pest problems would be resolved. When I return the device, I'm told that I can't get my refund back by Kholi, the shop assistant. I'm utterly disgusted, what a ripoff! Why purchase there if they can't give you a refund if you are unsatisfied.