Hello, I just had a colleague with the same model of phone and issue. Here's what I found. Sorry to necro this thread, I just found it via google and thought I could provide a bit more context.
They had 2 APN's configured. One for public mobile which was correct, and one for some sort of tether or something. So I deleted both of them and then a THIRD ghost APN showed up suddenly unexpectedly for telus.
So I deleted that one too until there were none. Entered in the public mobile one someone already provided in this thread. Rebooted, then everything started working.
I'm an I.T person by trade, not a phone person but here's my perspective of what might be happening in this situation. The sim public mobile gives people has the APN configured in most cases these days but the android os likely hung onto to that third old telus one. Voicemail and mms messages were likely being tried through that hidden APN instead of using the sim APN's and the fact that there's a bug where the OS will hang onto the old APN without showing it on the screen makes this tougher to troubleshoot. Maybe the first APN's server has to go down for maintenance or something before it stops trying that ghost APN and tries the next one which would explain why it is sort of intermittent.
Anyway, hope this helps anyone else googling in the future.
Have a nice day.
