Can't change to another SMS application even after uninstalling

Created by: Grah96

Two serious problems:

1. I try to use another text message application, change the default SMS application and... nothing - I can get no text messages and cannot send any. It's like Silence has silenced alternative SMS apps! I uninstall Silence... still I get nothing. Can't send or receive texts. I reinstall Silence (or SMS Secure as it was then) and it starts working again. It is like it is locked onto Silence's settings.
2. What I have also realised all my backup programs are doing nothing but pointlessly backing up the text messages I had before I installed Silence/SMS Secure. I can export plain text file containing the Silence stored text messages but then what? Do I replace the existing stock stored SMS file? Excuse my ignorance but how exactly As I think others have mentioned this needs to be a lot clearer and transparent please, and there probably should be some warning before installing.

This is extremely frustrating. Please advise how I can fix both of these problems. thanks Graham

Sony Xperia Z3 Android 5.1.1