Question: how do you change your voicemail password on iphone?
Answer: From a Home screen, navigate: Settings > Phone .
Tap Change Voicemail Password. If using an eSIM with a second line, select a line (e.g., Primary, Secondary, 888-888-8888, etc.) ... 
Enter the new password (4-6 digits) then tap Done. If prompted, enter the current password.
Re-enter the new password then tap Done.