Speech Recognition for Alphanumeric

Hi,

I am using Azure Communication Service with Cognitive Service for handling voice call scenarios (STT and TTS). One of our customer use cases requires alpha-numeric input in a workflow. The Azure Speech recognizer performs well for numbers and other patterns. However, when the user spells out alphabets for alphanumeric values, the recognition success rate is very low.

For example, the product ID pattern is like "P-43246". In most cases, "P" is recognized as "D", "B", or "3".

I have tested this on both mobile phone networks and VoIP. The success rate is significantly lower on mobile networks.

Is there any settings available to improve the recognition success rate?

Azure Services used:
ACS Phone Number
Azure Cognitive Service 
Event Grid Subscriptions

Thanks,

Aravind