Update prepare-buy-reservation.md

Author: mittalpri

articles/cost-management-billing/reservations/prepare-buy-reservation.md

@@ -17,7 +17,7 @@ Azure Reservations help you save money by committing to one-year or three-years
 
 ## Who can buy a reservation
 
-To buy a reservation, you must have owner role or reservation purchaser role on an Azure subscription that's of type Enterprise (MS-AZR-0017P or MS-AZR-0148P) or Pay-As-You-Go (MS-AZR-0003P or MS-AZR-0023P) or Microsoft Customer Agreement. Cloud solution providers can use the Azure portal or [Partner Center](/partner-center/azure-reservations) to purchase Azure Reservations.
+To buy a reservation, you must have owner role or reservation purchaser role on an Azure subscription that's of type Enterprise (MS-AZR-0017P or MS-AZR-0148P) or Pay-As-You-Go (MS-AZR-0003P or MS-AZR-0023P) or Microsoft Customer Agreement. Cloud solution providers can use the Azure portal or [Partner Center](/partner-center/azure-reservations) to purchase Azure Reservations. You will not be able to purchase a reservation if you have a custom role that mimics owner role or reservation purchaser role on an Azure subscription, you must use built-in owner or built-in reservation purchaser role.
 
 Enterprise Agreement (EA) customers can limit purchases to EA admins by disabling the **Add Reserved Instances** option in the EA Portal. Direct EA customers can now disable Reserved Instance setting in [Azure portal](https://portal.azure.com/#blade/Microsoft_Azure_GTM/ModernBillingMenuBlade/BillingAccounts). Navigate to Policies menu to change settings.