Grandma names 😡 I'm MAMA!

We never had a discussion but it was obvious my father in law wants to be called Papa, which is fine. But then he called his wife (my mother in law/ husband's step mom) Mama and signed their card like that also. The problem is that I want to be the only mom/ma/mama/mommy whatever! How do I bring it up??? Or do I even bring it up at all?! It's really bothering me 😕