When you first download the eSIM service and connect to a network you will be sent an SMS with your phone number in it. You can also get your phone number at any time by dialing the shortcode *133# from your phone in exactly the same way that you would dial a telephone number. However you must make sure that the eSIM plan is selected as the plan used to dial the number ( see the screenshot below ).
You will then receive a message on the screen with your phone number. You will also receive an SMS text message with the same information.