Assistance Required with Microsoft Teams Voice Auto Attendant External Call Routing

Good day

To help narrow this down, I would suggest checking the following areas:

1/ Verify the Auto Attendant resource account:

= Verified

2/ Confirm that the resource account has a valid outbound PSTN path:

= Verified

3/ Review Communication Credits or Pay-As-You-Go configuration (Calling Plan environments):

= Verified

4/ Check for outbound calling restrictions:

= Further investigating with vendor

To better understand the environment, could you let us know which PSTN connectivity method your organization is currently using?

Microsoft Calling Plan

Operator Connect - None

Direct Routing - SBC

Troubleshooting:

I called with a cell number to my direct line on teams, I can take the call and when I set forwarding then calls drops

error :

500 SIP;cause=500;text="General Routing Failure"

my next step is to create a new policy with and apply to one number testing number.

Good day Census,

Based on the behavior you've described, I would start by reviewing the outbound PSTN configuration of the resource account associated with the Auto Attendant.

While the Auto Attendant is clearly able to receive incoming PSTN calls, that does not automatically confirm that its resource account is authorized or configured to place outbound PSTN calls when transferring callers to an external mobile number. In fact, Microsoft has documented scenarios where Auto Attendants can successfully receive calls but are unable to transfer them to external PSTN destinations because of outbound calling configuration issues.

To help narrow this down, I would suggest checking the following areas:

1/ Verify the Auto Attendant resource account:

In the Teams admin center, navigate to Voice > Resource accounts and identify the resource account linked to the Auto Attendant.

From there, confirm that the account has a Microsoft Teams Phone Resource Account license assigned. Microsoft requires this license for resource accounts used by Auto Attendants that answer calls directly.

Reference: Microsoft Teams Phone Resource Account licenses

2/ Confirm that the resource account has a valid outbound PSTN path:

The exact configuration to review depends on how your organization connects to the PSTN:

• Calling Plan: Verify that the required Calling Plan and outbound calling configuration are assigned, and that any required calling credits or funding are available.
• Operator Connect: Confirm that the assigned service number and outbound calling services are active and functioning correctly.
• Direct Routing: Verify that the resource account has the appropriate Online Voice Routing Policy, PSTN usages, and routing to the SBC/carrier.

If you're using Direct Routing, Microsoft specifically notes that resource accounts using Direct Routing numbers require a valid Online Voice Routing Policy with the appropriate PSTN usages assigned.

Reference: Configure Shared Calling

3/ Review Communication Credits or Pay-As-You-Go configuration (Calling Plan environments):

If your organization uses Microsoft Calling Plans, it may also be worth checking whether Communication Credits or Pay-As-You-Go funding is required for outbound calls from the resource account.

In some cases, inbound calls to the Auto Attendant continue to work normally, while outbound transfers fail because there is no available funding for outbound PSTN traffic.

4/ Check for outbound calling restrictions:

In addition, I recommend reviewing whether any outbound calling restrictions are applied to the resource account.

Teams supports outbound calling restriction policies that can limit which PSTN destinations can be reached. If such a policy is in place, it could prevent transfers to external mobile numbers even though other calling scenarios appear to function normally.

Reference: Outbound calling restriction policies for Audio Conferencing and user PSTN calls.

One detail that stands out in your testing is that you can manually transfer a call to the same mobile number without any issues. That's certainly useful information; however, it doesn't necessarily mean the Auto Attendant resource account has the same PSTN permissions, routing policies, or outbound capabilities as the user who performed the transfer.

Because of that, I would compare the PSTN configuration assigned to the working user account with the configuration assigned to the Auto Attendant's resource account. Any differences there may help identify the root cause.

Finally, if your organization is using Direct Routing, I would also investigate the SBC routing and SIP transfer process. Microsoft has a dedicated troubleshooting article that covers Auto Attendant transfers to external PSTN numbers in Direct Routing environments, as SBC routing and transfer handling can sometimes contribute to this type of issue.

Reference: Issues that affect call transfers

To better understand the environment, could you let me know which PSTN connectivity method your organization is currently using?

• Microsoft Calling Plan
• Operator Connect
• Direct Routing

Additionally, if possible, please share the non-sensitive portions of the Auto Attendant resource account configuration (excluding phone numbers, tenant IDs, or any other sensitive information). That information may help identify which area should be investigated next.

I hope this points you in the right direction. Please let me know what you find after reviewing the above items, and I'll be happy to continue assisting.

Kind regards,

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