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.
- Modalities Service Settings > "Outbound Conversations" must be enabled for the corresponding Service.
- Your User account must be Online in MS Teams or the “Call on Behalf” Icon will be disabled in the Nimbus UI.
- Your Service must 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 “Call on Behalf” 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.
- With Task Parallelization enabled on your user, you can still use “Call on Behalf” while Parking another task simultaneously.
- All “Call on Behalf” sessions are subject to Dashboard Supervision, meaning that any Supervisor can listen, whisper OR barge-into an existing session.
Known Limitations
"Call on Behalf" features are treated like any Outbound Calls, and therefore underly all of the following limitations.
Outbound Task limitations
INC Outbound Task Limitations
KNOWN OUTBOUND TASK LIMITATIONS
General Outbound Call & Task limitations
Audio Modality:
-
Audio delay for outbound PSTN and UPN calls: There is a possibility for latency after establishing an Outbound Call between Agent and Customers. The delay is caused by Microsoft infrastructure and outside of Nimbus control. In order to minimize latency, an optimized approach was implemented and can be enabled by Luware Support 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.
Specific Call Features:
- Federated outbound calls are not supported. Any of “Outbound” type Flow Actions will return an error
- Preferred user routing is currently not supported for outbound calls. Preferred users specified will be ignored and the task will be distributed according to the configured Distribution Policy.
Specific: Outbound Call with Workflows
☝Please note that “General Task limitations above may also apply.
-
Supported Workflow Activities: Currently, all workflow activities except the following are supported in Outbound Calls with Workflows:
- “Voice Message”
Nimbus Design Notes
- Internal O365 User Search for Outbound Calls: The “Outbound Call” dial pad in Nimbus also allows to search for internal Nimbus 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.
- Reporting visibility of terminated Outbound Calls: 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.
- Nimbus Power BI Template: While the data related to Outbound with Workflow flows through seamlessly to the template, data related to Outbound Call with Workflow may appear in Service Overview > Inbound Calls widget in the template. Future releases will see improvements to this.
PSTN and Transfer limitations
INC Transfer to PSTN Limitation
☝Nimbus and related addons can only perform PSTN transfers according to Microsoft's licensing and constraints.
✅ As Administrator you need to acquire Microsoft Teams phone licenses
🤔Which PSTN licenses do I need to acquire?
Service Licensing
|
Target Service using any of the Microsoft | PSTN Connectivity options ▼ |
Licence to apply for Nimbus Services |
| Direct Routing |
“Teams Phone Resource Account” 🔎 See: |
| Calling Plan |
“Teams Phone Resource Account” license, plus
🔎 See: Microsoft Learn | Microsoft Teams Calling Plans 1 Only required for Outbound Call functionality, also see “Ahead notice Pay-as-you-go Calling Plan licensing changes” below. |
|
Operator Connect |
“Teams Phone Resource Account” |
User Licensing
| Target User | License to apply to Nimbus Users & Call Targets |
|
All Users, including … + Agents that handle Nimbus calls + Attendant Console transfer and consultation targets. |
“Teams Phone Standard”, each account having: |
☝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.
🤔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/ |
|---|---|
| Luware Helpdesk | https://helpdesk.luware.cloud |
| Cloud Service Status | https://status.luware.cloud/ |