Hi,
According to my research, in Outlook client, you can call your contacts via Skype or Teams:
- Double click a contact card.
- Click More > Call...

However, if you'd like to make telephone calls within Outlook client, I'm afraid there is not a build-in way to achieve it. You can refer to the suggestion of Diane in this
thread.
Hope this can be helpful.
Regards,
Aidan Wang
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