If he's shielding the identity of the person he's calling then there's a reason why. I don't know what brand of phone he's using but he's doing something underhand.
My husband is sending and receiving text messages from his number, it's only showing his phone number receiving and sending these text? Is there an app he is letting someone use his phone number to converse with?
is he sharing an apple account with someone else? If so they could be imessage texts from the other person.