Voicemail speaking extension

Is there a way to stop speaking of extension when you get into the voicemail like
if I dialed 100 and the call is not answered and then it goes to voicemail saying.
"The person at extension one zero zero is unavailable…"
I don’t want this ‘one zero zero’ speaking about extension.
Is this built in voicemail app or we can tweaks around.

Yes, record your own busy/unavailable VM messagfe via the VoiceMail menu you get by calling a featurecode number via telephone.