Your service provider would need to understand the mortgage service processes, identify issues with the current implementations (using existing management information and/or recordings), design alternatives (some of which may be better implemented using speech recognition technologies), test the design using Wizard of Oz simulations (if possible) and then come up with recommendations for implementation.
I would also recommend call analysis, to determine the way callers interact with the agents to identify the processes involved and what can be realistically automated. During the "Wizard of Oz" simulation (before deployment) a number of different dialogue/call flow variants can be trialed.
As a starting point see the following link for information with regard to good dialogue/call flow design/ practice: http://spotlight.ccir.ed.ac.uk/English_frames/html_files/dialogue_design_guide.htm.
This was first published in September 2005