Using extensions longer than 5 digits


I have a requirement to use 8 digit remote extensions. It all works fine but in FOP the extensions show up in the extension section and in the trunks section. I can manually go and delete the trunk buttons from op_buttons_additional.cfg and restart the FOP server, but that will only last until I need to add another extension. Is there a way of telling FreePBX that I want to use longer extensions and to not treat them as trunks?