As of now (May 2022) you cannot delete your call history in Microsoft Teams. Soon you might be able to delete your call history according to Microsoft 365 Roadmap Feature ID 94200. It says that we (might) get the option in June 2022 and it should be available for Teams on desktop, Mac and mobile. At the time of writing this there are no further details available e.g. where the button will be placed, screenshots, documentation.

Source: Microsoft 365 Roadmap Feature ID 94200 | Microsoft 365

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