On two different occasions now, I've heard details of text messages coming from someone to whom those texts weren't sent. This concerns me because I send a lot of texts to my boss for work, and I discuss information in them that is private. I've looked into remote tracking spyware apps and I'm not tech savvy enough to know what to be afraid of. Some of them make it sound as though anyone with access to your phone number can install anything they want and read every text and listen to every call.
What do I need to know about this kind of thing?