When you're ready to dial in, you can check the presenter screen for the current list.
For a Standard (Legacy) BrightTALK webinar you will find a list of presenter line options on the 'Prepare & Present' panel under the 'Dial in options' drop-down.
A BrightTALK Pro webinar lists the presenter dial-in options on the presenter screen as 'Dial-in numbers and PIN':
Please note: the availability of regional telephone numbers is subject to change. We recommend checking the presenter screen on the day of your live webinar to ensure you are using latest telephone numbers.