Hi, you can find some general help & troubleshooting on the UnitedCallouts download page.
This is the fix for your problem:
I can't get inside a building while I am playing a callout.
If you can't get inside a building, you need to install Open All Interiors which is linked in the UnitedCallouts.ini.
If you don't want to use it, set the callouts for Open All Interiors to false. (These callouts are set to false by default.)