Terms get confusing, but like executone said, you will have to contact your phone line service provider to have them add your 3rd line to be rolled to if the other is/are busy.
Nortel's term for HUNT GROUP is completely different than a Rotary Hunt from your provider. If you are just wanting to add your 3rd line to your Norstar hunt group, it should not be assigned to a phone.
Just re-read what I wrote, and it doesn't even make sense to me. Hard to explain from a keyboard, but am trying.
MarvO said it