I have an iPhone6s+. Whenever someone tries to call me, they hear a message saying "I'm sorry, the person you are trying to reach has a voice mail box that has not been setup yet. Please, try your call again later. Goodbye". I've used the phone to record a greeting, and I've hit *86 to verify that the greeting is set. The phone and *86 both say I have 3 messages. What's going on?