You can attempt to drop an incoming call. Dropping a call has different effects depending on the call type and other options:

If the call is a hunt group call, dropping the incoming call causes it to be presented to the next agent in the group or follow other hunt group settings (which can include presenting the call to you again).
If the call is a direct call to you, dropping it causes it to:
Go to your forward on no answer destination if set and enabled. See Forward On Busy/No Answer.
Else the call goes to your voicemail if available.
Else the call continues to ring (drop has no effect).
If the call is returning from being held or parked for too long you cannot drop it.

To drop an incoming call:

1.If the call is not the currently highlighted call on the display, use the up arrow up and down down arrow arrow keys to highlight it.
2.Press the Drop key. Depending on your particular phone this may be a soft key on the display or a physical key. You can also assign the drop function to a programmable key.