Lets say I have extension 3000 and its virtual 8000 and I have another extension 3001 that is going to call cover for 3000. Do I have to keys for both 3000 and 8000? If 3000 is on the phone and gets 2nd call it will roll to 8001. I am used to the UX5000 where you don't have to have a 2nd extension assigned to receive a 2nd call.