Net Blocker is a tool that allows you to prevent apps from accessing internet. It does not require root permission. Please read carefully the following descriptions before you use Net Blocker. You should carefully read the following descriptions before using the app. It does not ask for dangerous permissions like Location, Contacts and SMS. It doesn't ask for dangerous permissions such as Location, Contacts, SMS or Storage. You can therefore trust it not to connect to remote servers to steal your private data. Use it with confidence! This app uses the VPN framework from Android OS. If you turn it on, it will not allow you to use any other VPN apps at the same. It may also drain your battery. If the application does not have a network, some IM apps (such as Skype) might use Google Play services for incoming messages. To prevent IM apps from receiving your messages, you might also want to disable "Google Play Services". To save your battery, the Android OS Battery Optimization feature may automatically disconnect VPN apps from sleep mode. To keep the battery optimization working, you might need to add Net Blocker to your whitelist. Because Dual Messenger is only a Samsung feature and does not fully support VPN, this app cannot block Dual Messenger apps. You may have an app that overlays other apps such as blue filter apps. This could be the reason for your problem. These apps might overlay the VPN dialog so you cannot click "OK". This bug is in Android OS and must be corrected by Google through an OS upgrade. If your Android OS is not yet fixed, turn off light filter apps to fix it and then try again.