While covering all of the relevant information, aim to keep your voicemail to about 20 seconds. You definitely should not ever record a business voicemail longer than 30 seconds, and anything less than 10 seconds will typically mean that you are either speaking too quickly or aren’t providing all of the required information.
You would think there'd be app for that, but Apple doesn't allow third-party apps to access the microphone and the integrated Phone app directly. However, there are tricks within some apps and services to get around that limitation that can make you a mobile wire-tapping master.

Do you know of any other ways to send a call directly to voicemail? Do you know how to selectively send a call to voicemail on an iPhone? Tell us about it below if you do!
Techjunkie.com One sign that your phone calls are being ignored is how many rings before it goes to voicemail. Generally, the feedback ringtone will go through several cycles before the voicemail message comes up. If upon placing the phone call, it rings only once or twice and goes to voicemail then your calls are probably being declined. 443 is also the number to dial to retrieve voicemails. To switch voicemail off dial 1626. Voicemail deducts one minute from your Goodybag regardless of length of call (assuming you have minutes left) or, if not, costs 8p per call.