Voicemails not playing.

[BTSMGL]

I just tried to listen to a voicemail from my dad from 3 weeks ago, and I keep getting a message saying that it could not be played. Do voicemails expire?? My old Instinct HD kept my voicemails for OVER A YEAR without a problem.

Secondly, is there any way to "lock" voicemails I want to save?

Thank you to anyone who can help!