I just move the extruded object down and bool diff. Hmm sorry i can quite follow you.

I attached a new file. The whole is already cut out of there. But still i cant fillet the edges. Thats my question, why cant i fillet it.
If you would take a look at the file.


Edit.
Thank you.
^^ you edited it ^^. Ok now its works. But why cant i just only fillet the upper side?


Do you have any advice how to make the keys?
I would create small boxes for the keys. Array them around. Because the cell phone has some serious light effects (mayebe u know) i have to cut some space around the keys out to get a plane there, so that i can texture it at a later time.


edti2: Do you have any idea how i should create the speaker itself? Create a plane and cutting out the whole via a box and bool diff and array tool?