The default voicemail is neither the same nor different. It is carrier defined. I carry an iPhone and Android phone and, until customized, the message is the same on Verizon. Yes, I have carried two phones for years so this is not new.

With that said, yes, you are coming off as paranoid since there are other simpler explanations particularly since it corresponds to when the person is at work. If you have a concern about your husband then address it with him, not reddit. He could be cheating or you could be looking for a problem that does not exist. The phone is not the problem - it is the relationship that needs to be addressed.