You may be able to improve the accuracy of speech recognition by experimenting with a couple of GetInput XML features.
Speech recognition hints
Provide a set of hint words and phrases to improve speech recognition accuracy. This feature can greatly improve transcription accuracy of proper nouns, homophones (such as one and won), and domain-specific words rarely used in the general parlance. You can build a repository of words and phrases expected from speakers in the hints attribute of the GetInput XML element.
Experiment with the prebuilt speech recognition models. We recommend using the command_and_search model for command-driven IVR applications, and the phone_call model for more informal speech.