Do you have the same problem when the call is originated from the main office?
Other people have the same problem. See:
http://www.obitalk.com/forum/index.php?topic=10176.0Even more people have an echo problem.
Like the link suggests, make sure you are at the current firmware level.
You can replace the OBiLine adapter with an OBi110.
Here is another link:
http://www.obitalk.com/forum/index.php?topic=10749.0