Facebook recently launched the possibility to create a tailor made Call to Action-button (www.facebook.com/business/news/call-to-action-button). Add a button to your booking system from your facebook page by clicking the "Create call to action" -button on your Facebook page.
After this select "Book now" from the dropdown menu and add your booking system's address. Your DigitalBooker booking system is automatically responsive and thus works on all mobiles and tablets, you can use the same address for both your desktop and mobile call-to-action URLs.
Now everyone visiting your Facebook-page will see your "Book now"-button as the primary call to action.