When trying to setup voice mail greeting got this message "The operation couldn't be completed (com.apple.mobile-phone error 1034) Can anyone help me?

Having the same issue. Apple says it is FirstNet through AT&T. I called them and they had me do several different things including, resetting network settings, turning off Live Voicemail and then turning it back on, then accessing my voicemail through the “1” key, none of that worked. It goes back to when you try to change the greeting within voicemail it won’t let you, that is a software issue not a carrier issue as it seems that needs to work to tie your voicemail account to Live Voicemail. Issue is still not resolved and looks like Apple is passing the buck.