When you call 321 from your mobile, you’ll be asked to type the PIN into your phone and record your name and personal greeting (that’s what people will hear when they call through and can’t get back to you, so make it catchy).Once your greeting has been set, we’d recommend changing your Voicemail PIN to something more personal so you can easily access your Voicemail settings in the future. You can do this through the user options area of 321 (that’s option number 8 on the main menu).Your PIN can be any series of numbers between 4 & 9 digits, provided they are not sequential (e.g. 5678) or aren't a series of repeated numbers (e.g. 111).
Vendors like VirtualPBX sell hosted systems to offer businesses a simple method of creating voice networks. Businesses purchase subscriptions from a vendor and connect their IP phones to that vendor’s voice network.

And, once you record your voicemail greeting, all you have to do is provide your message in an .mp3 or .mp4 format to your phone provider, who will upload the message.
The phone you use to record your greeting – and your surrounding – can turn your carefully scripted greeting into an unprofessional mess. Background noise is terribly distracting, so choose a quiet room or parked car to make your call. Landlines, or a “wi-fi enabled” cellphone call, can provide much better connection quality than a standard cellphone. If you must use a cell phone, be sure to use a high-quality headset for the best clarity.