Adds note to the "Adding seats to your enterprise account" article (#51943)

Author: sophietheking

content/billing/using-the-enhanced-billing-platform-for-enterprises/adding-seats-to-your-enterprise-account.md

@@ -10,6 +10,8 @@ permissions: The enhanced billing platform is available to all enterprise accoun
 shortTitle: Add seats to your enterprise
 ---
 
+>[!IMPORTANT] If you pay by invoice, you need to contact your account manager in {% data variables.contact.contact_enterprise_sales %} to add seats to your enterprise account.
+
 If you have access to the enhanced billing platform, you can add seats to your enterprise account through the "Licensing" page. To check if you have access, see "[AUTOTITLE](/billing/using-the-enhanced-billing-platform-for-enterprises/about-the-enhanced-billing-platform-for-enterprises#how-do-i-know-if-i-can-access-the-enhanced-billing-platform)."
 
 {% data reusables.enterprise-accounts.access-enterprise %}