Voice messages can be up to five minutes long. When your voicemail is full, you can no longer receive new messages.
Jan 21, 2008 · Where "(your phone number)" is your 11-digit phone number (including 1 and the area code), and "15" is the number of seconds (from 5 to 30 in 5 second increments) that you want your phone to ring before going to voicemail. (The default seems to be 10 seconds.) You can thank me later. 😉 (Hat tip to Bradley!)

To avoid missing important calls in those situations, it is better if you know how to set up voicemail on Android or iPhone so that you can be away from other businesses or engagements without having to worry about missing any important calls.
Follow the instructions and press that number. You will be asked to delete your current Voicemail greeting. Click on the ‘Yes’ button that appears on the screen if you want to remove that. You can save your new recorded Voicemail greeting or can use the default recorded option. From the home screen, select the Phone app. Note: Alternately, you can set up voicemail by selecting the Phone app then selecting and holding the 1 key. Select Keypad, then select the Visual Voicemail icon. Select Start. Select Ok. From any Home screen, tap the Menu key. Tap Settings. Tap Call settings. Tap Voicemail. Tap Voicemail again. View the voicemail number. Press and hold the 1 on your device’s dial pad to call and connect to your voicemail. Press the star * key to access the main menu. Press 4 to access the mailbox options. Press 7 to change the language of the voicemail prompts to either Spanish or English.