I accidentally deleted the outgoing voicemail announcement that was my deceased father's voice. Can it be recovered?

Is there a way to recover deleted outgoing announcements on a landline? My mom has saved my dad's outgoing voicemail announcement since he died 3 years ago. It defaulted to the standard memo recently when the landline was repaired, but his voice was still on the system. I could listen to it as a saved announcement but there was no way to make it the active one (even after calling comcast). I was trying to figure out how to restore it today when I accidentally reset it and now his voice is nowhere on the system. My mom will be absolutely devastated. Is there any way to get it back?