Annoying messenger pop up when launching messages+

[JLS1979]

I use messages+, I am not switching to messenger, not now, not ever, no matter how many times I am asked to make it my default SMS app, I will not. How can I get that heads up message to stop showing up EVERY SINGLE time that I launch messages+? I have wasted hours on Google looking for answers and have tried every suggestion I could find, nothing has worked. I have uninstalled the messenger app for fb, I have attempted to uninstall the stock messenger app on the phone (are they the same thing b/c they were 2 seperate app icons?), NOTHING has worked. I have turned off peeking and notifications, I have tried EVERYTHING. I do not want to select "no" to that stupid message every time I want to use my preferred SMS app. I am so angry with this I want to switch back to my old phone. It is embarrassing that someone actually got paid to make the decision to harrass users this much with a stupid annoying message. How many times does someone have to select "no" before they gets the message?