add'l permission

Author: b-ahibbard

articles/azure-netapp-files/includes/create-volume-permission.md

@@ -12,6 +12,9 @@ ms.author: anfdocs
 ---
 
 >[!IMPORTANT]
->If you're using a custom RBAC or IAM role, to create or update a volume, you must have the `Microsoft.Network/virtualNetworks/subnets/read` permission configured.
+>If you're using a custom RBAC or IAM role, to create or update a volume, you must have the following permissions configured:
+>
+> * `Microsoft.Network/virtualNetworks/subnets/read`
+> * `Microsoft.Network/virtualNetworks/subnets/join/action`
 >
 > For more information about permissions and to confirm what permissions are configured, see [Create or update Azure custom roles using the Azure portal](../../role-based-access-control/custom-roles-portal.md).