It is not very complex task to remove and assig VNET IP address for Azure based virtual Machine if you employ PowerShell scripts. In order to use PowerShell for Azure, you may need to download and install Azure PowerShell program commonly found here: 

http://azure.microsoft.com/en-us/documentation/articles/install-configure-powershell/

First step after AzurePowerShell installation is authentication with your Azure Account via Add-AzureAccount PowerShell command. We use 10.0.0.6 as your internal VNET IP for assignment to VM called vmName in the example below. Pleas note: it is improtant to add your VM when you auto-provision to a specific VNET set up before you start provisioning your Virtual Machine.

Please find steps below required for successful VNET IP swap.

Step 1. Add-AzureAccount

Step 2. Import-Module azure

Step 3. Get-Azuresubscription

Step 4. Select-Azuresubscription "Pay-As-You-Go"

Step 5. Get-AzureVM -ServiceName "serviceName" -Name "vmName" | Remove-AzureStaticVNetIP | Update-AzureVM

Step 6. Get-AzureVM -ServiceName "serviceName" -Name "vmName" | Set-AzureStaticVNetIP -IPAddress 10.0.0.6 | Update-AzureVM