Caller ID feature helps you hide your helpdesk number and shadow it with another number. To enable this, please navigate to Admin-> Phone-> Manage caller ID (a blue option near "buy number") and add the numbers you wish to use for masking. Once you've added the number, please select the helpdesk number you want to hide and scroll down to the call masking section. You can now add the number you wish to shadow this with and this number would mask your helpdesk number.