The Call on Behalf feature allows service users to impersonate and make calls as the service itself. This feature is also known as "Call As" or "Calling as a Service".
PRECONDITIONS
- Enterprise Routing Contact Center Outbound Calls are an Enterprise Routing and Contact Center Service Type feature. "Outbound Conversations" must be enabled via Modalities Service Settings for the corresponding service.
- The user must be Online in MS Teams or the “Call on Behalf” Icon will be disabled in the Nimbus UI.
- Services using this feature need to have a PSTN number assigned in order to dial out to an external number. Otherwise only UPN (internal users and services) can Also see the "Known limitations" section below.
🔍 Note that Basic IVR Services (User assignment type = None) are excluded from this feature.
Call on Behalf from Within the Portal UI
"Calls on Behalf" can be manually initialized from the Nimbus portal:
- Navigate to the My Overview, Services Overview or Attendant Console and click on the telephone icon next to the service you want to call on behalf as.
⮑ A teams dial out popup opens. You can now dial a number.
💡 Before calling, you can still choose between all services which are available to you (and fulfill the preconditions above). - To start the outbound conversation, click on the Call icon .

☝ Note: User Presence, Nimbus Status and UI interactions
MS Teams Presence:
- Remember that you must be “Online” in MS Teams or the “Call on Behalf” Icon will be disabled in the Nimbus UI.
- Being DND will not disable the button. User related "Busy Available/ Away Available" settings (made via Distribution Service Settings > Conversations Distribution) such as “available when busy” are also ignored.
Nimbus-specific interactions:
- Contact Center When users are in persistent RONA or in (extended) After Call Work time, Outbound Service Calls are not possible.
- Any blocking Nimbus User States will also disable the call button, e.g. when there is an incoming/connected call or other blocking tasks such as ACW.
- Call On Behalf sessions are subject to Dashboard Supervision, meaning that a Supervisor can listen, whisper or barge-into an existing session.
Known Limitations
INC Outbound Task Limitations
KNOWN OUTBOUND TASK LIMITATIONS
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Audio delay for outbound PSTN and UPN calls: There is a latency after establishing an outbound call between agent and customer. The delay is due to Microsoft. In order to avoid latency after call establishing, an optimized approach was implemented and can be enabled by Luware Support in Extensions Tenant Settings for your tenant.
☝ Note that enabling the optimized approach requires testing on your tenant as Microsoft has not yet rolled out dependent functionality globally for all MS Teams tenants. - PSTN Licensing: When the selected service doesn't have a phone number (PSTN license) applied, the dial pad is disabled. A dial out to a UPN (e.g. a MS Teams User or Service) is always allowed.
- Reporting visibility: Terminated outbound calls are currently not reflected on any reporting view (Reporting, Dashboard, or Power BI). This is currently by design as (repeatedly / manually) started or scheduled Outgoing Calls could affect and skew service KPIs.
- Internal O365 Search: The outbound call dial pad in Nimbus allows to search for users. In order to retrieve and call to O365 contacts, a tenant admin needs to grant User.Read.All consent for all Nimbus users, as described on the Nimbus User Permissions page.
INC Transfer to PSTN Limitation
☝Out of the box, Nimbus and related addons can only perform PSTN transfers according to Microsoft's licensing and constraints.
🤔Which PSTN license do I need to acquire?
As of 2023, "Microsoft Teams Phone Standard" licenses are no longer supported by Microsoft. Previously, those licenses were viable for Nimbus. Regardless if you are using Direct Routing, Calling Plans, Operator Connect, the "Microsoft Teams Phone Resource Account" license is now always required.
Your Setup | Required License |
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Direct Routing |
"Microsoft Teams Phone Resource Account" |
Calling Plan |
"Microsoft Teams Phone Resource Account" + "Microsoft Teams Domestic Calling Plan" or "Microsoft Teams Domestic and International Calling Plan" or "Microsoft Teams Calling Plan pay-as-you-go" + "Communication Credits" (if these aren't already included as part of your plan) |
Operator Connect |
"Microsoft Teams Phone Resource Account" |
☝Please note that Luware staff cannot give recommendations on which license plan is best suited for your needs. Depending on your scenario, additional Teams App licenses may be required. Exact details are to be discussed with your Microsoft contacts.
🔎Also see: https://learn.microsoft.com/en-us/microsoftteams/teams-add-on-licensing/virtual-user
🤔How does PSTN licensing affect Service and call transfers?
Assuming that the initially called Service has (no) PSTN license assigned - the following scenarios may unfold:
Scenario A - Service A has a PSTN license. Transfers to other Services occur.
⮑ The PSTN license carries over throughout transfers to other Nimbus Services B and C.
⮑ As the license carries over, a PSTN transfer to an external target is possible from either Service.
Scenario B - Service B has no PSTN license. A Transfer to Service C occurs which has a PSTN license.
⮑ The customer skips over Service A and manages to reach Service B instead.
⮑ The PSTN license is missing on Service B, so nothing is carried over to Service C.
⮑ Even if Service C has its own PSTN license, a PSTN transfer to an external target is not possible.

🌟Learnings:
- Nimbus will use the PSTN license – and create a (transfer) Session – from the FIRST Service responding to a call.
- Regardless of how many internal Service transfers are performed thereafter, the FIRST Service PSTN license remains in effect.
- If a PSTN license is missing, the transfer task will fail and be treated accordingly by the System.1
- Even if a Service being transferred towards has a PSTN license, it cannot be added in post, as the Call Session is already ongoing from the first-responding Service.
✅ For your licensing needs this means: If you require PSTN transfer functionality, you'll need to ensure that this Service is handling all your incoming calls.
- For ONE first-level / Front Desk Service, you'll need a PSTN license for this particular Service.
- For MULTIPLE first-level Services scenario, you'll need PSTN licenses for all first-level Services.
1🔎 Assumption: Workflow takes the normal “Exit” Announcement route and Service Session will conclude with a “Transfer failed” outcome. For more details on analyzing your Reporting results, refer to Nimbus Reporting and Static Dimensions > "Service Session Outcomes"
☝Note that handling and tracking of running cost for PSTN licenses is outside of the Luware support scope. If you however require assistance in extending and/or configuring your Nimbus Services for PSTN, our support will gladly assist you:
Luware Support Address
Luware Website | https://luware.com/support/ |
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Luware Helpdesk | https://helpdesk.luware.cloud |
Cloud Service Status | https://status.luware.cloud/ |