I have found this statement:
"Be careful, its not easy getting the front cover off when you've not done it before, I damaged the microphone by trying to lever it off from the bottom, luckily the Nokia Service Centre fixed it for me under warranty, however they wouldn't fit a new cover. First, use a T6 screwdriver to remove the screws, you then need a device for prizing open the top cover, I used an old sim card. From the bottom gently pull the top cover upwards just enough to make a gap to insert the removing device, then slowly edge the device along the left side of the phone, this is where the clips are, gently manoeuvre the cover off from this side, do the same thing to ease off the right side if it's proving difficult."