You might say you are aware of the challenges their company is facing and you believe you can help. If you have been recommended by someone they trust, this can be your message.
Use an upbeat and friendly tone of voice, and be sure to address your prospect by name as well as give your name and contact information.
Then follow up. Keep track of the content of the voicemails you leave so you can refer back to them and build on the content if you have to leave more voicemails. Practice persistence and keep calling back.