Multiple time data store using pubnub?

I have developed a android chatting application in which users can talk to only customer care team subscribe to five specific channel i.e Laundry, Food, HomeServices etc. I am using PubNub to full-fill this requirement. But now, I have faced some issues regarding multiple entries of the same data. I am storing chat messages data in my server when users send messages to customer care(at the time of listening) or vice versa(at the time of publishing). But now, I am facing two serious issues if no customer care executive is online data is not getting stored in the database and if customer care executive account is logged on multiple devices it store the chat message twice in the database sent by the customer.