Added a note re CSP subs.

Author: anosov1960

samples/manage/azure-arc-enabled-sql-server/modify-license-type/README.md

@@ -39,6 +39,8 @@ The script accepts the following command line parameters:
 ```PowerShell
 Get-AzSubscription | Export-Csv .\mysubscriptions.csv -NoTypeInformation
 ```
+> [!IMPORTANT]
+> If you are setting License type to PAYG in the CSP subscription(s), the subscription resource must have a consent tag enabling perperual pay-as-you-go billing. Without the tag, the command will fail. The consent tag is `SQLPerpetualPaygBilling`:`Enabled` and can be adding using [Azure portal](https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/tag-resources-portal), [PowerShell](https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/tag-resources-powershell) or [CLI](https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/tag-resources-cli).
 
 ## Example 1