How to Disable the Voicemail Password on an iPhone
Cellular service providers offer a voicemail password to help protect your privacy. While it's not recommended that you disable this feature, most providers offer a way to turn off voicemail passwords directly from your iPhone. Verizon customers can't do this, though you can set up your iPhone so you don't have to enter it manually when you want to collect your messages. If you're using Visual Voicemail on an iPhone, you can't disable the password, but you can change the password in the iPhone's Settings.
If you are an AT&T customer, you can disable the voicemail passwords simply by calling your voicemail. If you have new voicemail, press "*" to skip to the Main Menu. Press "4" to access Personal Options, then "2" for Administrative Options and "1" for Password Options. Press "2" to disable your voicemail password. Follow any additional prompts you hear before disconnecting. Use the same menu options if you want to enable the password option later.
If you're a Sprint customer, use the Skip Password option to disable your voicemail password. Here's how: Press the "Voicemail" button on your iPhone's Phone app and follow the prompts to access the Main menu. Select "Change Personal Options," then select "Administrative Options." Follow the prompts you hear to turn on Sprint's Skip Password option.
T-Mobile offers a variety of shortcodes to access different features, one of which turns your voicemail password on and off. Turn on your iPhone and enter "#PWO#" or "#796#" to turn your voicemail password on or off. If you just want to reset your password, dial "#PWD#" or "#793#" from your iPhone.
If your iPhone is with US Cellular, call your voicemail and press "4" from the Main menu for Personal Options. Press "4" again to modify your personal options, then press "2" to enable the Skip Password option.
While Verizon doesn't have an option to disable passwords, the company does suggest a work-around. Simply add a "Voicemail" contact to your iPhone's Contacts app, including the password. Use "\*86" as the phone number, followed by two pauses and then your password. To add each pause on an iPhone, tap " +\*# " and select "Pause." Each pause is displayed as a comma, so if your password is "1234," the number will appear as "\*86,,1234" on your iPhone. After you call this number the first time, tap the "Information" button beside the number and select "Add to Favorites." This way the number will always be on your iPhone's Favorites screen so you can quickly find it.
IPhone Visual Voicemail
To change the password protecting your iPhone's Visual Voicemail feature, launch "Settings" from the homescreen, select "Phone" and then tap "Change Voicemail Password." In iOS 8.0, there isn't a way to disable the password requirement for Visual Voicemail.