Google messenger has this feature. I found it extremely useful earlier when I was using it. Suppose 3 mobile numbers are added under a contact XYZ. Now while creating a group for texting, I start adding people to it. If I need to add more than 1 number under XYZ in a group text, earlier selected number should not appear again. It creates confusion as I cannot know the numbers by heart and same mobile number can get added multiple times in a group text.