Solved Incoming PSTN calls to a Teams recipient will not disconnect after external caller hangs up

[ahbladmin]

I'm back here today after self medicating yesterday i.e. I fixed my own problem on the same day that I posted.

Our instance is version 18.0.1880 in Azure with the 3CX supplied domain of xxxx.my3cx.ca and we just got incoming/outgoing PSTN to Teams working yesterday.

During testing, I discovered that PSTN calls that rang out to Teams voicemail would result in 5 minute voicemail messages even though their messages themselves were much shorter. I learned that 5 minutes is the maximum duration of a voicemail in Teams which indicated that the call was not disconnecting when the caller hung up. I confirmed this by using my cell to call my Teams account and saw that Teams session stays active after my cell hangs up.

I believe the following two lines in the activity log shows the failure on disconnect:

25/08/2021 10:43:53 - [CM503003]: Call(C:185): Call to <sip:[email protected]3cx.ca:0> has failed; Cause: 487 Request Terminated/INVITE from 127.0.0.1:5080

25/08/2021 10:43:53 - [CM503003]: Call(C:185): Call to <sip:[email protected]:0> has failed; Cause: 487 Request Terminated/INVITE from 127.0.0.1:5063

I did the same test where the the Teams side hangs up and the cell side disconnects properly. This happens both with the Teams Windows client and on the Yealink desk phone (yes, one of a very few environments probably using desk phones of which has been a bit of a nightmare for anyone else that has discovered the bugs with the Teams client on physical phone - but that is for another thread).

Thanks, George

 

[NickD_3CX]

Hi George,

These 2 lines don't show a call failure. I realize that the word "failed" can mislead a bit, these messages just state that an extension was ringing, then the Caller hung up before the receiver answered.

This though doesn't change the fact of what you described.

Please do me a favor and try something:

1. In your 3CX Management Console, go to Dashboard and press on "Number of calls in use". This shows you all active calls of 3CX in real-time.
2. Make an incoming call via PSTN and make sure it goes to the Teams Voicemail. It should show up in the Active Calls at this point
3. Leave a 10 second Voicemail, then hang up.
4. After you hang up, do you still see the call connected in the Active Calls list, or does it disappear when the Caller hangs up?

 

[ahbladmin]

Hi NickD, thanks for responding again to my first and second ever posts. I just did the test above and I can confirm that the call terminates in 3CX (i.e. Numbers of calls in use) immediately after the PSTN caller disconnects but the Teams session remains active. It's like Teams does not receive the disconnect signal/code from 3CX.

To add some more information that may help, we are already using Teams Calling with a third party SIP provider through the SIP provider's own SBC and this problem doesn't exist. The one difference between this setup and the one with 3CX is that the SIP trunks are different. The vendor is the same but the trunk used in the production environment is a "Teams" trunk and the second trunk used for 3CX is a "normal" SIP trunk.

I'm not a SIP expert so I wonder if there are any specific settings in the configuration of the SIP trunk that is required to support Teams Calling. The SIP provider is ThinkTel.

Thanks, George

 

[NickD_3CX]

Hi Geroge,

OK, let's check if the transactions are happening correctly on the 3CX side. We can see where we are at after this.
Please do the following:

1. From Dashboard --> Activity Log --> Settings, set it to "Verbose"
2. Go to Dashboard --> Services, select everything, then press "Restart"
3. Log back into the Management Console
4. Replicate the same scenario (call in, leave call to go to VMail, leave 10 second message, hangup)
5. In the Management Console upper-right corner, press "Support", then "Generate Support Info"
6. You will receive an email on the admin email account you have set, with a link. Download it, place it in a file sharing service of your choice (GDrive, OneDrive, Dropbox, WeTransfer, etc...) and send me the link in a PM.
7. In the PM, also include the call details like what the Caller number was, which Extension the call is forwarded to, etc.

We should be able to determine from that if 3CX sent a BYE message and if Teams acknowledged the receipt of this message.

 

[NickD_3CX]

After discussing with the team, it was pointed out that Teams Voicemail should be disabled for users that are synced with 3CX.
This should be done when you execute the Powershell scripts generated by the 3CX Management Console, as per the instructions here.


As an extra piece of information, in V18 Update 1, we plan on allowing reject calls from the Teams Client to follow "busy" Forwarding Rules of the 3CX Extension that the Teams User is synced with.
This means that if the Teams Voicemail is disabled, the call will be rejected, but the 3CX Voicemail can takes its place (or any other Forwarding Rule you want for that matter.).