You're forcing them to leave voice mail? How last century of you.
I just mumble my contact information into their voicemail and then when I don't hear back from them in the next 3 days, I fire off an angry email to their direct supervisor about their department's incompetence, demanding free replacement equipment.
Works every time, and I am highly valued for my skills.
i love looking at my phone and seeing it just say "Florida" is calling