To see previous conversations with the customer, click the blue label at the top of the chat area in your conversation:
Previous conversations with the same customer on the same channel open above the current conversation. Scroll up to see them.
If the customer sends new messages when you have scrolled up, you will see a number appear on the arrow icon in the bottom right corner. To move back down to the active conversation, click the arrow icon:
Note: You can only see previous conversations when you have an ongoing conversation with the customer. After you end the conversation, you will not be able to see previous conversations until your next conversation with the customer.