2 Listen to Your Voicemail from Another Phone
For the most part, listening to your voicemail is something that you do on your own iPhone. But most carriers actually let you “call into” your voicemail from basically any number. All you have to do is call your own phone number and let it go to voicemail.
Once you hear the greeting, press the star or pound key to interrupt it — AT&T, Sprint and T-Mobile will use the star key, while Verizon uses the Pound key.
Once you enter your voicemail PIN, you can listen to your messages. (Voicemail PINs are resettable in Settings > Phone > Change Voicemail Password.)