Inquiring minds want to know

When having voicemail messages stored and/or downloaded on a previous iPhone with one carrier and then “supposedly” upgrading to the latest and greatest iPhone “14 Pro Max” 😞2 years ago signing with a new carrier those voicemails did transfer during initial download to the new iPhone. However, with every new iOS apple update have now just disappeared. As such, does the same suggestion advised contact carrier hold true for retrieval of these messages or because they were downloaded and not just saved will they be in the cloud? I’m unable to open iCloud messages to find out!

Any direction would be greatly appreciated.

Thx Michelle