Looks like they are just cleaning house of lesser-used models? This came via mail last week.

  Back in June 2023 and November 2023, we announced the following models will be deprecated on June 13th, 2024:
   gpt-3.5-turbo-0301 
   gpt-3.5-turbo-0613
   gpt-3.5-turbo-16k-0613
  We noticed that your organization recently used at least one of these models. To help minimize any disruption, we are extending your access to these models for an additional 3 month grace period until September 13th, 2024. After this date, these models will be fully decommissioned.