My freinds world doesnt show up in the multiplayer menu when cellular dat on

See my freind and i both have cellular data on . I say my freind to join the world so that i can join. THE WORLD DOESNT SHOW UP IN THE MULTIPLAYER MENU. So i said my freind to check his cellular data and network strenght it was good and even my was good. So thats the problem when everything is good and fine the world doesnt show up. It happens only in cellular dat not in wifi. Please fix this i dont have wifi to play with freinds.