Hi, I don't think to have an alphanumeric slot (AMAZON.AlphaNumberic) is reliable for spelling words. Yes, it could work many times when testing directly in the AWS console but when you introduce the error of the voice traveling across the PSTN, the audio quality is not good and you start getting errors that you didn't have before. That is a problem with voicebots over the telephone network.
On the other hand, it is more reliable when using a slot of the type AMAZON.NUMBER, actually you are using it for the CutomerNumber. So I don't know if it's possible for you just to get numeric part of the PO then add the prefix STOCK later (unless you have too many options for prefixes).
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Henry Zambrano
Powernet Global Telecommunications
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