Two extensions = one device state

I have phone with two configured extensions.
101
00101

first one remains in queue, secondone used for local inbound and external calls.

Problem: When user dials external number from 00101 his extension 101 remains in queue with “Not in use” status.
How could I make both extensions unavailable if only one of them is busy?

solution:

exten => 101,hint,PJSIP/101&PJSIP/00101&Custom:DND101&Custom:DND00101,CustomPresence:101,CustomPresence:00101
exten => 00101,hint,PJSIP/101&PJSIP/00101&Custom:DND101&Custom:DND00101,CustomPresence:101,CustomPresence:00101