You can use custom rules to set condition
- IF direct dial is called, play an announcement and disconnect
- All other calls connect normally (for example calls coming from Call queues, IVR Menus, Auto-Receptionist)

Here is step-by-step:
- Admin Portal > Users > click on your name > Phone > Call rules and voicemail > in the top right corner you should see +Add rule > Create Custom Rule

• name the custom rule
• then select only the 2nd option -> Calling me at > select your direct number
• in the top right click on "Ring my devices" and change it to "Play an announcement"
• Done