SravanKrA wrote:
Probably you are referring to the voicemail service provided by your carrier, since that works differently from Apple’s Live Voicemail feature. With carrier voicemail, messages are stored on the carrier’s server and can behave in ways that depend on their system — for example, some carriers automatically delete messages after a certain number of days, or after you listen to them. On the other hand, Live Voicemail on the iPhone doesn’t delete messages once you’ve read or marked them as read. They stay in your Phone app until you manually remove them, giving you full control over when they’re gone.
I think there may be some confusion here between. Live Voicemail and Visual Voicemail.
Visual Voicemail has been around for years. It's what does the transcriptions of voicemail that you see in Phone>Voicemail. It's my understanding that, though it requires some support from the carrier, it's built into the iPhone. It cannot be turned off from the phone.
Live Voice Mail is a much newer feature. It allows the user to see the message as it is being left and allows them to pick up the call if they want to. It can be turned off from the phone.
Set up your voicemail on iPhone - Apple Support