Dial/knob doesn't do anything

This is the fourth ultrasonic humidifier I've purchased over the last 10 years and the only one that doesn't really work. It does put "vaporized" water into the air, but the knob which has symbols from "a little moisture" to "a lot of moisture" doesn't do anything. The amount of moisture coming out does not change. I called Customer Service the day after I bought it and they said they wouldn't fix it or send me a new one and my only recourse would be to return it to where I bought it. The $30 ultrasonic humidifier I put in my daughter's room functions so much better than this one which I bought for $50.