We put a lot of effort into trying to get people not to leave messages on the old house phone (long story, there was some reason I forget why we couldn't turn the voicemail off). Messages with words in don't work. Even if you make them 10 minutes long and full of "Please do not leave voicemail here, we won't hear it" repeatedly, people will sit through it and then leave a message. We eventually settled on something that sounded like a very noisy modem, which mostly worked. I have no idea whether people would recognise modem noises these days though, especially if this is for a mobile number...
I don’t know about you, but I’m shocked every time I listen to a voicemail message left for me by sales reps, prospects and even clients. They are filled with ‘um’s’ and ‘ah’s’, they ramble on and on, they leave no compelling reason for me to call back, and they almost always leave their number so fast that I have to listen to it two, three, sometimes four times to make it out!

I love your class Annemarie! Thank you so much! Truly, as a non-native English speaker, I spent a lot of time to deal with it and took a whole lot of energy to try NOT to have conversation through phone as much as possible, however, it is so inevitable in our daily life especially at work.
d. Utilizing Ambiguity Over Clarity: When setting up your voicemail greeting be direct and to the point. Tell callers your information, a brief greeting, and direction—i.e. “Hi, this is Jim Shamalam (from Iron Industries). Sorry I can’t take your call right now. Please leave your name number, and a brief message and I’ll get back to you as soon as possible. Thank you.” This is ideal, as you inform callers and let them know what they should do to ensure a return call. A lack of direction can lead to callers leaving incomplete messages (lacking contact or other information) or even callers hanging up without leaving a message altogether.