Finding MMS on my mobile iPhone 15pro can’t find in settings so I can change it it

JohnFro_2736781 Why do you even need to change those settings?

Settings > Mobile Service > Choose SMARTY from your list of sims > Mobile Data Network 

HOWEVER, It’s probably already set correctly for you, so be careful if changing it, as you may input incorrect settings 

What’s the purpose of changing the settings ?