Callers getting message that voicemail not set up

I have a report from one of my customers . They say that, randomly, people who call in through the IVR and push the number to go to an extension are getting a message that says something like, “The person you are calling does not have a voicemail box set up.”

They cannot give me a time or number the person is calling from, so I can’t really check my logs.

Has anyone ever experienced this?