You can use MiiTel Phone Mobile to play your voicemail and check your messages.
It's available for both iOS and Android.
How to play a voicemail.
1 Tap [History] at the bottom of the screen.
2 Tap [Voicemail] to show only voicemail history.
3 Tap the voicemail history you want to play.
4 Tap [Play Voicemail].
5 When the message "It's playing" appears at the bottom of the screen, the voicemail will be played.