Where are VVM files stored? What extension do they use?

My LG K51 VVM started acting up by not downloading VM. (I use the VVM App as storage for messages with out getting transcripts). I restarted my device and it downloaded messages, but then as soon as I listened to them they deleted themselves.

I spoke with Tech Support and they didn’t really know, suggested a few things to try, and would call back next day. Never did. So I acted on their suggestion to remove and reinstall the Visual Voicemail App.

Tragedy ensued! It deleted 2 years and 5 months of saved messages, many of which I need for an upcoming court case. Sadly, I should’ve known better than to listen to this Tech Support Person, and now I no longer will unless I get US Tech!

So, Where are VM’s downloaded to the phone stored, what is their extension and what software/app can I use to retrieve them?