If you have Huawei device with OS 5, click here.
This setting is specifically for Huawei devices on OS 8.0. Note, this is required for blocking calls as well.
Follow these steps:-
1. Navigate to your phone settings
2. Apps & Notifications
6. Launch > Disable Manage automatically - see picture below
For certain Huawei devices, you need to tap 'disable', at the bottom: