I have checked this internally and below is an update.
You should use "chat completions" instead of "completions" with these recent models. As documented here Azure OpenAI Service models - Azure OpenAI | Microsoft Learn, the 0613 revision of gpt-35-turbo is only compatible with that newer chat completions operation: "Completions" is now considered a supported but "legacy" feature for older models--and this is true for platform.openai.com in addition to Azure OpenAI.
If a customer absolutely must use the older completions operation instead of chat completions (e.g. because they've already made significant investments into fine-tuning or ChatML prompt engineering), they'll need to use a supported model/version as described on the matching documentation page here: Azure OpenAI Service legacy models.
Let me know if that helps or have any further queries.