Overview

You may experience an issue that calls are not working from Verizon Operator, with a message: "Welcome to Verizon Wireless. Call cannot be completed as dialed, as the called party is busy."

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Prerequisites

• Screenconnect access
• PSX access
• Hepic access

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Solution

To start with troubleshooting, we will need call samples. Open a ticket with Support, making sure to describe the issue and any symptoms you observe, and add at least two call samples in the following format:

• Calling From Number:
• Calling To Number:
• Date of call: dd/mm/yy
• Time of call: xx:xx am/pm (time zone)
• Result: ex: dropped call, garbled audio, etc.
• Trouble observed: Inbound or Outbound

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When dealing with such requests:

1. In a Screenconnect VM for the region log in to Hepic with your AD credentials.
2. Search the call samples provided and check the SIP flows for any issues.
3. Proceed based on your findings. Make sure to check the Known Cases below. 

Known Cases

Cancel coming from AT&T

Calls can be canceled by AT&T. For example:

Call is canceled by : 12.194.xxx.xxx

2023-02-20 23:14:43 +0800 : 12.194.XXX.XXX:5060 -> 192.168.39.27:5060 TOS:184
CANCEL sip:XXXXXXXXXX@192.168.39.27:5060 SIP/2.0
Via: SIP/2.0/UDP 12.194.XXX.XXXX:5060;branch=<...>
CSeq: 934417474 CANCEL
From: "WIRELESS CALLER" ;tag=<...>
To: "User XXXXXXXXXX"
Call-ID: <...>
Max-Forwards: 68
Content-Length: 0

As this is an issue with AT&T:

1. Open a case with AT&T.
2. Once we have the answer, action whatever is needed on our side, and request the customer to apply any changes per AT&T if the configuration has to be done on the customer side.

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Based on the troubleshooting, the Support team will either take action to fix the issue on our side, escalate to ATT, or reach back with findings and any next steps required from you.

Verification

Once the root cause is fixed, try to replicate the issue to confirm that it is no longer there.