When your marketing voicemail goes on for too long, you can lose the contact completely. Or, even if they do stick with you through the whole thing, they may lose the main point of why you’re calling. Keeping your voicemail between 20 and 30 seconds is enough time to make your elevator pitch without over-talking.
Why should they respond to you? How will your product or service help them? Will it make their job easier or allow them to get more done in less time? These are examples of real benefits and your sales voicemails need to contain something similarly beneficial.

I touched on this earlier, but it's worth repeating. Keep your voicemails short and sweet. Very few — if any — of your prospects are interested in spending multiple minutes listening to you make small talk or rattle off your offering's features and benefits.
After leaving four or five messages without receiving a response, you should stop calling – at least for now. Don't expect the courtesy of a call back from a hiring authority. Unless they have a need for someone like you, it is not likely that they will call you back. Don't take it personally. If you are looking for a job or soon may be, join Tony Beshara for a FREE webinar: The Top 10 Reasons You Might Have Trouble Finding a Job (and How To Combat Them).