How to save a voicemail you never want to ever lose?

A family member of mine recently passed away but I still have their voicemail on my iPhone 4 because I just can't part with it. Obviously it won't stay in my phone forever and I'm due for an upgrade soon. There has to be a way to save it to email, digital format to a hard drive or some other format. I can't stress how much this means to me. Any help is greatly appreciated.

Get another phone on video record and play the voicemail on loudspeaker on your phone and record the voicmail then send it back to yourself.

You can save them by downloading iBackupBot and save it that way, and it will be saved to your computer, heres the link that shows you how you can do that
http://pinglio.com/2012/03/how-to-save-your-iphones-voicemails-for-safekeeping/