Add banner indicating retiring, no new customers.

Author: aspreadbury

articles/communications-gateway/prepare-to-deploy.md

@@ -10,6 +10,9 @@ ms.date: 04/26/2024
 
 # Prepare to deploy Azure Communications Gateway
 
+> [!IMPORTANT]
+> The Azure Communications Gateway service will retire on October 30, 2025, and no new customers are being onboarded. To prevent any service disruption, please transition to another [Microsoft Teams Direct Routing certified Session Border Controller (SBC)](/microsoftteams/direct-routing-border-controllers) solution before October 30, 2025.
+
 This article guides you through each of the tasks you need to complete before you can start to deploy Azure Communications Gateway. For Operator Connect and Teams Phone Mobile, successful deployments depend on the state of your Operator Connect or Teams Phone Mobile environments.
 
 The following sections describe the information you need to collect and the decisions you need to make prior to deploying Azure Communications Gateway.