Welcome to Microsoft Q&A! Thanks for posting the question.
You are getting this error as you are not passing the correct model name to the api request.
As mentioned in the document you need to pass the deployed model name as "model" in the request body.
You can get the deployed models under "deployments" section on open ai portal. (see the screenshot below)
I have tested this with a resource in East US 2 region with a deployed model and it works as expected. (see below)
Please let me know if you still see any issues.
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