Removing my phone number from the gmail accounts I no longer control

At a past job we needed to do some log in & app testing so we created a number of email addresses. The gmail accounts needed a phone number and I used mine. I've left that job and no longer have access to the list of email addresses but would like my phone number removed from them.

I expected, within Google's security settings, to see a "your phone number is also used on these accounts..." and to be able to unlink them.

Has anyone ever done this?
Know where I need to go?

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