There is a way to block another player from contacting you in the game. You can do it by tapping their name in the game and selecting block. You can also perform the same action by tapping their player name in the chat, then profile, and selecting the red “Block’ button.

Okay, but how can I unblock someone?

If you’d like to unblock a player, tap your player name in the upper left side of the screen and tap the “Blocks” tab. You will see a list of players you have currently blocked. Select the ‘Unblock’ button on the right side of their name.