How do we transfer a call direct to voicemail using the Poly Edge E350

How do we transfer a call directly to voicemail using the Poly Edge E350 phones. We can only find the ability for a regular consultive transfer which then rings on there phone (NOT WANTED) and a blind transfer which also rings there phone. We don’t want that. We want to send direct to voicemail...which is a feature on the desktop app but not the phone! How do we get the direct to voicemail softkey to show up on the phone??