Boolean modiifiers are not working properly

I have made a model of a mobile phone and i want to cut out a small piece from tit to make the screen. When i use the Boolean modifier, it gives me strange results, although the fact is that the modifier is at the top. I have been tweaking the settings but nothing has worked. Here is my .blend file: help on this file.blend (361 KB)
Here are some images for quick reference: . As you can see, the resulting model has strange faces in it and the lower left of the screen still has a complete face . How can i correct this? Are there any ways other than Boolean subtraction that i can use to cut out rounded faces?


one problem is that your cutting object has internal faces. try removing those first.

also before you apply the modifier, make sure all normals are outwards on both objects

this method will not give a good result. you will be able to make a hole in your object but the topology will be bad