I can't find chat settings in the messages settings.
On both my Samsung phones its like this
Messages icon (blue circle, white square and 3 dots) tap on there and top right corner you will see 3 vertical dots, tap on those, that brings you to a Dropbox menu, choose settings, at the top of that page you should see chat settings, tap on that and the next page should have a box saying Default message type tap that and you get 3 options, automatic, text or multimedia, chat. You need to click on text or multimedia.
Hope this helps I would post screenshots but its not an option on here sorry