If after 2 solid phone/voicemail/email attempts (which counts as 6 touches, not including any drip emails or LinkedIn messages/connection requests that they may have gotten in between calls 1 and 2) I’ll leave a 3rd voicemail message (followed by an email, of course) that simply says something along the lines of:
After recording voicemail messages you want, you can make some simple editing tasks with the embedded audio editor, or transfer it to CDs for permanent collection by using its built-in CD burner. Moreover, this method is the most common method that is now being used in recording voicemail, since VoIP services have high demand on the main stream.

The duration of the global semiconductor shortage just keeps getting shorter -- and with it, investor confidence in semiconductor stocks like Advanced Micro Devices (NASDAQ: AMD), which closed down 6.1% Tuesday. If you recall, market researcher International Data Corporation (IDC) predicted last week that the dearth of semiconductors, which has hamstrung markets for everything from PCs to automobiles over the past year, will begin easing later this year. Speaking at the Code Conference in Beverly Hills, California, reports CNBC, Su pointed to a number of new semiconductor manufacturing plants coming online over the next few months as evidence that, while supplies will remain "likely tight" through the first half of next year, the chip shortage may end sooner than some investors expect.
Give them a reason to call you back. In both voicemail messages, did you noticed how I mentioned new information they might be interested in? That will grab their attention more than simply introducing yourself, thanking them and asking them to give you a call if they have any questions. Come from a place of helpfulness by giving them something to look forward to and that will solve a problem.