Update identity-model.md

Author: FarrukhGhaffar

articles/communication-services/concepts/identity-model.md

@@ -25,7 +25,7 @@ Azure communication service identity model works with two key concepts.
 ## User Identity / Mapping:
 Uniquely identifies a user through a user-identifier, which is generated by Azure Communication Services when a user is created. External identifiers such as phone numbers, users, devices, applications, and GUIDs can't be used for identity in Azure Communication Services. You can create Azure Communication Service user identities for free. Charges are only incurred when the user consumes communications modalities such as a chat or a call. Your users identity can be mapped to Azure Communication Services user Identity in 1:1, 1:N, N:1, N:N configurations. A user can participate in multiple communication sessions, using multiple devices, simultaneously. Mapping between Azure Communication Services user identity and customer's private user identity is kept and maintained by the customer. For example, customers can add a `CommunicationServicesId` column in their user table to store the associated Azure Communication Services identity.
 
-## Access Token: 
+## Access Tokens: 
 After a user identity is created, a user is granted with the capability to participate in communications using chat or calls, using access tokens. For example, only a user with chat token can participate in chat and user with VoIP token can participate in a VoIP call. A user can have multiple tokens simultaneously. Azure Communication Services support multiple types of tokens to account for users who require full access vs limited access. See the [Access tokens](#access-tokens) section in this article. 
 
 Access token have following properties.