T-Mobile: T-Mobile has a similar story to tell as Verizon. Instead of allowing you to set up a specific basic voicemail, it instead directs you to Apple to set up Visual Voicemail. I dont see anything that you have written when I try to set up voicemail on my new Iphone11. I tap on voicemail and the only option is 'Call voicemail' … then it doesn't accept my mobile number.
Press the voicemail button on your phone or dial *98/*99 to access the voicemail menu. 2. Press 0 for Mailbox Options and then press 5 to change the password. 3. Enter your new password of at least four digits and then press #. 4. Re-enter the new password and then press #. Turn on notifications for my voicemail. 1.

Enter a name for the new greeting and then tap Save. Change your greeting. To use a different greeting that you've already recorded or switch back to the default greeting: On your Android device, open the Google Voice app . At the top left, tap Menu Settings. In the Voicemail section, tap Voicemail greeting.
If you’ve already created a custom voicemail on your iPhone, you can tap Play to see how your voicemail sounds. If you’re interested in creating a new message, tap the Custom button. From here, you can start recording your message by tapping Record and tapping Stop whenever you’re finished. Once you’re finished recording, tap on Play to make sure the message comes across as you’d like and hit Save (in the upper right) to save it as your voicemail.