iPhone bug alert: No notice when voicemail full

With an Apple iPhone running iOS version 11.3, there is no notice if your voicemail fills up. Callers will get this notice: "The mailbox is full and cannot accept any messages at this time. Goodbye."

A previous version of iOS would tell you when your voicemail was full, but only if you actually went into your voicemail (i.e. just opening the Phone app was not sufficient to get the notification).

To reduce your voicemail so that your phone can accept new messages, you must delete some messages then scroll to the bottom and clear the Deleted Messages. You may also want to check Blocked Messages and delete them as well. I believe that deleted Blocked Messages will go into Deleted Messages.