Facebook users have been quite upset with the company as recently they have made it a requirement for US users to user their Facebook Messenger app to chat with other Facebook users. Well it looks like there is a trick that allows you to keep chatting in the normal Facebook app if you have an iPhone.
The trick seems simple enough, when in the normal Facebook app go to chat and when you are prompted to install the messenger app go ahead. While the messenger app is being installed switch to the app store and stop the installation or delete the app.
Once you reopen the normal Facebook app you should have your chat capability back and no more annoying prompts. Of course this could all change if Facebook updates their app to look harder for the messenger app. Let us know if this trick works for you!