1) Getting prospects on the phone can be challenging as they often don't answer or screen calls. Leaving voicemails is time-consuming and prospects likely won't call back.
2) Effective voicemail messages are brief (20-30 seconds), educate the prospect on your value by focusing on how you help clients or common pains you address, and include your contact details twice.
3) It's best to call multiple times without leaving a message initially, then follow a call cadence of voicemails and follow-up emails before moving on to other contacts if no response is received.