You can update this through SQL. In SQL Enterprise Manager, expand your current CCM database. In the TelecasterServiceParameter table, find the PreDial parameter and copy the GUID from the fkTelecasterService column. Open the TelecasterSubscribedParameter table and search based on the fkTelecasterService GUID that you copied. You can update those rows that have a 1 for the Value column to a 0. You can do this manually or with an update query.
Hope this helps. If so, please rate the post.
Brandon