The number of participants you may have join via telephone and the number you may have join online are defined by your subscription plan. Please contact your Company Administrator for further clarification on this.
All Callbridge accounts can have up to 1000 telephone participants in one conference call. For more information about large-sized conferences, please take a look at the following support article link: How to Successfully host a Large or Event sized Conference
Additionally, all accounts also offer up to 25 web conference participants. Our Deluxe and Enterprise subscriptions allow up to 100 web participants to join via internet and 8 of those would be able to share their video or screen. You can compare all plans here: https://www.callbridge.com/pricing/