TF/Azure- Change the existing NSG with a new one requires deassociation . Please let me know how I can do the same in TF

Terraform Providers Azure
1

I have the below code, please pay attention to the “azurerm_network_security_group.example” resource block where I have declared the NSG name as a variable. The first pass of deployment is completed with default values and now I am passing a different NSG name as variable input for the next deployment. My understanding is that TF will destroy the existing NSG which has old name also automatically de-associate the nsg from the subnet. But it is not the case once I run the command and getting an error that NSG can’t be deleted as it is already associated with the Subnet. Could you please help me how this can be resolved . thanks.

Here is the error

azurerm_network_security_group.example: Destroying... [id=/subscriptions/7fbdc229-f0b8-4d8f-829d-7d6488df93b1/resourceGroups/myNewResourceGroupName/providers/Microsoft.Network/networkSecurityGroups/testnsg]
╷
│ Error: deleting Network Security Group "testnsg" (Resource Group "myNewResourceGroupName"): network.SecurityGroupsClient#Delete: Failure sending request: StatusCode=0 -- Original Error: Code="InUseNetworkSecurityGroupCannotBeDeleted" Message="Network security group /subscriptions/7fbdc229-f0b8-4d8f-829d-7d6488df93b1/resourceGroups/myNewResourceGroupName/providers/Microsoft.Network/networkSecurityGroups/testnsg cannot be deleted because it is in use by the following resources: /subscriptions/7fbdc229-f0b8-4d8f-829d-7d6488df93b1/resourceGroups/myNewResourceGroupName/providers/Microsoft.Network/virtualNetworks/tftestvnet1/subnets/tfsubnet1. In order to delete the Network security group, remove the association with the resource(s). To learn how to do this, see aka.ms/deletensg." Details=[]
│

main.tf

# Configure the Azure provider
terraform {
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~> 2.65"
    }
  }

  required_version = ">= 0.14.9"
}

provider "azurerm" {
  features {}
}

resource "azurerm_resource_group" "rg" {
  name     = var.resource_group_name
  location = "EastUS"
  tags = {
    environment = "Production"
    team        = "azuredevops"

  }

}

resource "azurerm_virtual_network" "tftestnetwork" {
  name                = "tftestvnet1"
  resource_group_name = azurerm_resource_group.rg.name
  address_space       = ["10.0.0.0/16"]
  location            = azurerm_resource_group.rg.location
  subnet {
    address_prefix = "10.0.0.0/24"
    name           = "tfsubnet1"
    security_group = azurerm_network_security_group.example.id
  }
  
  tags = {
    environment = "Production"
    team        = "azuredevops"
  }
}



resource "azurerm_network_security_group" "example" {
  name                = var.nsgname
  location            = azurerm_resource_group.rg.location
  resource_group_name = azurerm_resource_group.rg.name

  tags = {
    environment = "Production"
    team        = "azuredevops"

  }
}

variables section

variable "resource_group_name" {
  default = "myTFResourceGroup"

}
variable "nsgname" {
    default = "testnsgfromvaraible"
  
}