How to disable notifications about phone being in DND mode?
This is usually caused by applications such as peel remote. As a solution try disabling the application.

Try disabling the app:


To disable an app, go to Settings √ Apps √ Applications √ Peel Smart remote then choose option.
Alternatively deactivate it in drawer; Go to the app drawer, tap Edit, you will see minus sign besides the given app at the top-right of the screen: When you select the minus sign, you will see the selected app no longer in the background. You will also stop receiving any updates which also stops unnecessary drain on resources.