Say that your prospects want to speak to the sales department and so when they realize that they have reached the right department and hear the voicemail messages, they will be compelled to leave their contact details so that the sales team can reach out to them later. They will be relieved.
Hi, you’ve reached (your name) office. Either I’m away from the desk or on another line. Please leave me a brief message with your name and contact number so I can call you back. If this is an emergency, call me on (your cell phone number).

The biggest barrier is actually getting them to leave the voicemail in the first place. Don’t get in your own way by recording a long, drawn-out voicemail greeting that might do more to convince them to hang up than actually leave a message.
You may additionally want to bear in mind that people might be calling you from their cellphones, and a long message can use up someone’s valuable cellphone minutes. Some voicemail systems have the option of pressing a key like the pound key to immediately start recording a message; you may want to consider the funny or long message only if you have this option available to callers. Another point of consideration when recording an answering machine greeting is who is likely to call. If you’re job hunting, for instance, you may want to drop the funny salutation for a while, and use a more standard and businesslike greeting, unless you’re applying for jobs as a comic. Is Amazon actually giving you the best price? This little known plugin reveals the answer. Some answering machines utilize cassette tapes.