You have the option to block that user!  This can be done by pressing the “Block” button on the screen that is shown when a user goes to resign a game.
 
(This button only shows up for rematch games or “Friend” games (where someone finds another user by their team name.)
 
If another user is harassing you or other players in chat, please let Customer Experience know  by creating an in-game ticket, so we may take appropriate action.  If you can grab a screen shot of the interaction, please include that.
 
  1. To create a ticket in-game, tap the three lines at the top of the screen.
  2. Tap the "Customer Care" button to open the FAQs page.
  3. Scroll sown and tap the "Chat with us" button.