Tailor the action after a dialog state failure according to call center status, other options for completing the task, and the importance of receiving a response
When, based on the number of reprompts given or counts of noinput/nomatch/help, callers appear to be in trouble, there are several design options (Lewis, 2011):

• Switch to touchtone (especially if the problem appears to be related to speech recognition – e.g., multiple nomatches)
• Point the callers to an alternative means of accomplishing their task (e.g., a website) – especially if there is no call center or it isn't open
• Transfer to an agent (if there is an open call center)
• Offer a callback option (if the call center isn't open or if the expected wait time is unusually long)
• For non-critical dialog steps (such as asking callers if they want something repeated), accept the failure and keep going. It might sometimes be necessary to provide a transitional prompt, e.g., “No problem, let's move on.”

Lewis, J. R. (2011). Practical speech user interface design. Boca Raton, FL: CRC Press, Taylor & Francis Group.