Unable to change feature code settings

When I open up the feature codes I am able to highlight in the field that I want to change but I am not able to type anything in the field. I have tried several different browsers and they all do the same thing. I am trying to change the general call pickup from *8 to *7 but unable to do so.

You need to uncheck the Use Default check box next to the feature code to be able to override the default.

Thank you very much.