Marty uses WhatsApp with his family, but when he gets a call from someone, it has been displaying the wrong contact. Leo says that WhatsApp looks to the phone's contacts in order to identify who's in it. Marty's personal number may have gotten added to another contact, and all he needs to do is delete his number from that specific contact and it should be fine. Leo says it's probably just a messed up database.
Starting over is one way to fix this. He could wipe the phone and then reload his contacts. It may also be getting the information from another database, like Facebook. This is a common problem with contact lists.