How I hacked hundreds of companies through their helpdesk (medium.freecodecamp.org)

Check this out- TextNow uses a users phone number as a users account number.

The pin is default 1234.

All you need to port a number is the account number and pin.

Verified, works. Also I got a free phone.

Basic version: you can sign up for internally shared services with an email account ending @company.name, the account gets sent a link to verify and give access.

But some @company.name addresses -- commonly support@ -- route the email responses to a publicly accessible page, eg a bug report.

So you sign up to Slack with that support@company.name email, get the link for access to the company Slack from the support website, Bob's your Uncle!