Hi @F15 and welcome to the community!
I'm not quite sure I follow. Do you need to remove a screen lock because you are sending your phone to service? A screen lock is removed under Settings > Security > Screen lock. If your display is not responding to touch then you might be able to navigate to this menu using an OTG-cable and a computer mouse, which will make a cursor appear on your display so you can navigate the menus in your phone.
If you simply wish to reset the phone you can do so by performing a software repair using Xperia Companion.
