@scot46: As voicemail is a feature that is provided by your network, I recommend reaching out to them directly to see if they're able to shed any light on this for you.
To give you an idea of when the voicemails were left, try heading to the Phone app > Recents, and looking for any recently received missed/forwarded calls. As the Recents tab is organised via date and time, and displays the number/contact details of the caller, this should hopefully contain the information you were looking for.
