Specific Calls Trigger multiple lines.

[vanguard08]

Head, meet wall.

Company A has an area code of 636, probably arbitrary but just as a note. When Company A dials any of our numbers, the receiving phone acts as if it's receiving 3 calls virtually simultaneously.
Company A does not experience this with any other company including other offices of ours. Our office experiencing this only sees this behavior when called from Company A.

T23G Yealink phone's are in place with 3 Line BLF's configured. The physical BLF line lights 'light up' upon receiving a call from 636* and very quickly proceed to engaging the other 2 lines.
In most cases: when line1 is answered, the call ends, same with line2, but when line3 is answered the call may continue as normal.

Attempting to find a work-a-round I've:

1. Created a brand new extension, provisioned a new phone, and altered inbound rules appropriately.
2. Instead of setting inbound rules to send DID traffic directly to "reception" extension, I created a ring group with Reception Ext. as the only member and sent traffic to that Ring Group.
3. Created a dummy extension, sent inbound traffic there and forwarded it to the reception extension.

It does not appear any of my silly attempts to fix it have been successful. It only happens when Company A calls this specific office. And this office only has the problem with Company A.
I've attached a snippet of what the call log looks like when one of these calls come in.
I can't really think of anything else to try. Any ideas, crazy or not?

 

[leejor]

The Call Logs are not going to give you a lot of information. You need to examine the Activity Log to see what is happening with the incoming call.

 

[vanguard08]

Hmm. Okay let me try to pull some more appropriate logs. The log I pulled had no apparently relative information in it nearby the same time stamps. This is the first time I've had reason to even check logs more than the regular event and call log. I'm probably just doing it wrong.

 

[leejor]

Those are the sorts of logs you want to look at, but for the specific oncoming call. So...if you have the number in question call, Set appears to get 3 calls, then check the Activity Log. You may want to set the log to show more detail, but se what you get with the default settings. You should see the call come in from the provider (Invite), route to ?, then end. once you hang up.

 

[YiannisH_3CX]

Hello @vanguard08

The first thing i would is to check where the issue is coming from before trying to resolve it. To do so start a wireshark capture and have Company A call you. Then open wireshark and see if there are 3 calls coming from the provider or just one.
If there are 3 calls then call your provider and ask them what they see from their side. If there is just one call coming to the PBX then check the activity log. You may also want to get familiar with the Bin Log Viewer as it contains more details about the internal operation of the PBX.
https://www.3cx.com/docs/3cx-log-viewer/