It rings to all zebras that are logged into the phone app, there's no way to forward the incoming calls to a single zebra as they all have the same extension. There's likely someone who is designated to pick up phone calls so I wouldn't worry overly much. However if it gets to ring 4 or 5 then it'd be a good thing to answer. Just answer it how you would answer the phone if you were doing receptionist work.
Seasonal opu/ship idiot here. They hired me three weeks ago and I have no idea what to say if my Zebra rings. The person who tried to "train" me said to ignore it. Is it really a fucking guest??????