Where is the file to manually edit mobile data settings ?

Hi there, I'm desperately fighting to get mobile data. Since the mobile data switcher is always greyed out, I can't even long press to edit the settings (tried lots of tricks in other posts, from reboot to factory reset... nothing works). So my question is : where can I find the file which contains the mobile data settings ? If I edit it manually, maybe I could get some data... Thanks a lot for your help !