Update-AzureVM : BadRequest: The virtual network ID cannot be null or empty

Error while trying this:

Get-AzureVM -ServiceName ServiceName1 -Name VMName1 |
    Set-AzureSubnet -SubnetNames StaticSubnet |
    Set-AzureStaticVNetIP -IPAddress 10.0.0.4 |
    Update-AzureVM

any idea?