Lentek Pest Contro Ultrasonic Pest Repellers- 4 Pack

I ordered a 4 pack from this company because I had a friend who said this product really worked and I had a spider problem that wouldn't go away. The package arrived on time and said 4-pack on the outside packaging. My son opened up the outside packaging and there was only one unit inside. So, I go to website to see if I can just get 3 additional units and my only option is to return for refund, of course, I have to pay shipping. This may have been a factory mistake but I certainly will not purchase from this vendor again.