S6 no notification of reply to messages inside the conversation

Hi, hope someone cant help with a solution. Im new to samsung phones. Im loving my S6. However when using the facebook mesenger app i cannot find a setting to alert me i have a reply to a message whilst that message chat windows is open, so if i am not looking that my phone i often miss replies from friends etc..

If i send a message and close the app i always get a notification when someone replies or sends a new message

Is there a fix for this

thanks in advance

Paul