Being in a team you can chat with other teammates using the team's instant messaging system. You can access this feature by going to the CHAT tab in your team window.

All the messages you send are visible to all the members of your team. Once sent, a message can't be deleted. However, you can hide other players' messages if you find them inappropriate. To do it, tap on the message and select REPORT in the pop-up menu. The message will become hidden from you (it will still be visible for other team members), and your team's leader will receive a report and will be able to take action if they deem it neccessary.