tomc,
Just saw your post in the Feature Request sub-forum. It's a nasty workaround, but the second call can be disconnected via the OBi Web Page. After you have hook-flashed, placed the 2nd Call, and decided to disconnect the call, you simply click on "Remove" for Call 2 in the Status -> Call Status page in your OBi. If you are always at your computer, you could simply bookmark this page for easy/fast access.
Not the solution you wanted, I know, but it does seem to work.
pc44