Rollover to line 2 if line 1 busy?

[tritch]

I'm wondering if I can turn off Call Waiting, it might cause this to happen that way?

UPDATE:
In the VPanel, there is an area under Beta > Misc = FXS Port Control where the option looks to enable what we are asking for. I have shut off Call Waiting for both lines with Busy forward to VoiceMail default. If this does what it implies the outcome should be exactly what, at least what I am looking for.

If this doesn't work, just log into your ATA with the "user" credentials and then go to tab "User 1" or "User 2" as needed and turn off the CW setting as highlighted in the attachment.