Can I change my status to 'please contact to check availability' ?

If you leave your availability/ calendar blank (unknown), company members will be able request an update on your availability.

If you are in a staff job, you can select that option whilst marking your calendar as 'unavailable'. This will advise people to get in touch with you to discuss your availability.  

TIP: Although it's good to encourage people to contact you directly, a blank calendar can suggest that you're not currently looking for work so wherever possible it's best to add in your currently availability status.