1. From standby mode or the Phone application on select Sprint phones, press and hold the Envelope key on your phone until the display reads Connecting… (your Sprint phone number), or press and hold the 1 key until the display reads Connecting… (your Sprint phone number).
After setting the number on your voicemail, you must also record a personal voicemail greeting. Follow the steps below. Start the Phone app. if you don’t see the numeric keypad, tap “Keypad” at the bottom of the screen. Tap and hold the “1” for about two seconds until the phone automatically calls voicemail. Immediately tap “3” to access voicemail settings. Listen to the options. On most voicemail systems, tap “2” to start the process to record a new greeting. The current personal greeting will play; then tap “2” again to record a new greeting. Say the greeting you want, and tap “#” when you’re done. To save the greeting, tap “1.” The personal voicemail greeting has been set. Hangup the phone. How to setup voicemail using a Visual Voicemail Applications

Website: https://www.telus.com/en/support/article/manage-use-record-mobile-greetings
7. T-Mobile Visual Voicemail. Not all people actively use voice mail. In case you have to use it sometimes, you can download T-Mobile Visual Voicemail – it allows you to send infrequent voice mail messages.