You know what I do when I'm in your situation?
Go to your customers office and challenge them to point out any electronic device in their office that is older than 7 years. this includes: calculators, clocks, coffee warmers, computers, anything.
I'm willing to bet the cumulative age of all of the devices is less than the age of that voicemail.
Then ask him which devices he can do without. I'm willing to bet the voicemail is not one of them.
*******************************************************
Occam's Razor - All things being equal, the simplest solution is the right one.