Add-Ons have some special features that are not available on the WP SMS Pro (Pro Pack)
Provide a range of SMS marketing features for your online store. These include the ability to launch SMS campaigns, receive abandoned cart SMS notifications, manage SMS notifications, and receive local shipping SMS notifications.
Easily receive SMS messages from your subscribers or clients with the WP SMS Two-Way add-on. This feature allows you to enable incoming messages on the inbox page.
Fully compatible with the Twilio features such as managing incoming, outcoming calls, scheduling calls, etc with WordPress!