It's not really a customer support line, it's more of a redirection to a customer support line. There's no actual queuing going on, and if the dialed number doesn't pick up it's going to go to their voicemail, rather than the support voicemail to which after-hours calls go.

You can support call queueing and call duration so that it doesn't go to the user voicemail. This is just a simple example to get you started.