Hi Dano14, can you help us to help you by giving more context to your reported issue?
What Switch are you dealing with? how is the connection between your host, VoIP Phone and Switch? is PoE involved? can you provide logs (Switch/Phone)? What VoIP Phone is involved? is the host using some saving-energy settings applied to its Ethernet interface? ...and so on.
The more detail you can provide the better the Community can help you to diagnose your issue avoiding waste of time.