Late device return

I’ve tried several times to figure out how to return the modem. The  website would say click on device you’d like to return and no options ever showed up. And every time I had called to return it. I had waited about an hour to speak to someone! Now I’m being charged an absurd amount! I really just want to get this thing Returned without having to pay that ridiculous amount. I work everyday and can’t be waiting on the phone for hours to speak to someone.