There are multiple ways:
- Visit https://broadsoft.mit.edu and authenticate.
If you see your phone number listed (check the dropdown menu if there's more than one number), your number is on Broadsoft.
- Open your Zoom app.
If you see a phone icon, your number is part of the Zoom Phone Service.
- Visit https://voip.mit.edu.
The client type and where you manage it will tell you if it's Zoom or Broadsoft (the example below is Zoom).