Lumen- diversion header call forward

[lightfoot]

We are self hosted v18.0 update 7 and cannot forward calls to mobile numbers that originate from the same mobile provider. The SIP trunk is provided by Lumen and works great other than this issue.

Example-

originating number --> destination number --> forwarded number

the originating number and the forwarded number are with the same mobile provider (tested with t-mobile)

It has been tested with 'Use Call Deflection (302)' option checked and transferring to the extension that then forwards to the mobile number, and also tested transferring directly to the mobile number- both unsuccessful, Lumen does not see a diversion header. On successful calls (calls that the originating and forwarded number are with different mobile providers), the outbound caller ID is transferred correctly and shows the originating number to the forwarded number.

Digging thru the Lumen SIP docs I've found this-

**Call forwarding with Diversion header SIP Trunking supports call forwarding from a customer PBX. For the original CALLING TN to be presented as the CALLING TN to the final destination, Lumen supports the use of the Diversion header. The Diversion header is included in the INVITE message from the customer PBX.**

I know Lumen is not a preferred SIP provider, but is there a solution or workaround?

TIA

 

[YiannisH_3CX]

Hi @lightfoot

At the moment 3CX does not support the diversion header. I would recommend using a supported provider. If 302 is not supported then there is no other solution

 

[lightfoot]

Thanks for the response- does 'at the moment' mean that it is in the works?

 

[lightfoot]

BTW- CenturyLink (Lumen) is on your supported list, just not on the preferred list.

 

[YiannisH_3CX]

Thanks for the response- does 'at the moment' mean that it is in the works?

It means it's one of the things being considered for the next major version. Still very early though.

 

[laudatio]

According to the latest regulation in the Czech Republic, it will be necessary to use Diversion Header for all forwarded calls to mobile networks on 1 January 2024. In test mode, it is already running on 6.5 million numbers.

 

[lightfoot]

Thanks for the response. We are in the United States, will this regulation make 3CX support Diversion Headers in an upcoming release or risk losing Czech customers?

 

[leejor]

The fact that this is working for numbers not on the same mobile network suggests it may be the mobile provider that is causing the issue. Do you have the same issue if the call originates and terminates on a mobile network other than T-Mobile?

 

[lightfoot]

It only happens for calls on the same mobile network- tested with Verizon, T-Mobile, and ATT

 

[laudatio]

The fact that this is working for numbers not on the same mobile network suggests it may be the mobile provider that is causing the issue. Do you have the same issue if the call originates and terminates on a mobile network other than T-Mobile?

Yes this

The fact that this is working for numbers not on the same mobile network suggests it may be the mobile provider that is causing the issue. Do you have the same issue if the call originates and terminates on a mobile network other than T-Mobile?

At this time 19.9.2023 call forwarding to T-Mobile is not possible any more. Other two operators O2 and Vodafone will block forwarded calls later this year. This is due to the huge amount of mobile number masking fraud.

 

[laudatio]

Thanks for the response. We are in the United States, will this regulation make 3CX support Diversion Headers in an upcoming release or risk losing Czech customers

 

[laudatio]

From my position, I cannot assess the deployment scenarios of all 3cx customers in our market.

I can say with certainty that the need to use a diversion header when redirecting to mobile is now and will be in the future mandatory in our market and that there will be no exceptions.

In our case, we have handled 1 million calls on our PBX from 2015 to present and the current situation is a major complication for us.

 

[laudatio]

From my position, I cannot assess the deployment scenarios of all 3cx customers in our market.

I can say with certainty that the need to use a diversion header when redirecting to mobile is now and will be in the future mandatory in our market and that there will be no exceptions.

In our case, we have handled 1 million calls on our PBX from 2015 to present and the current situation is a major complication for us.

 

[leejor]

Have you spoken to one of the mobile providers to see if they have a definitive explanation as to why this is not working. They could have something in place to block forwarded calls from one of their own. Of course you will have to hope you get passed onto to someone with technical knowledge. The service clerk you first reach will have no clue as to what you are talking about.

 

[lightfoot]

Lumen support has reached out to T-mobile support using whatever channels they have and T-mobile responded that due to the amount of call spoofing they (T-mobile) do not allow a forwarded call from off their network but using a number registered on their netowrk to go through- and I'm assuming the same is true for Verizon, ATT, etc. T-mobile also said that using a diversion header should work but neither Lumen or 3CX support that.

 

[laudatio]

Have you spoken to one of the mobile providers to see if they have a definitive explanation as to why this is not working. They could have something in place to block forwarded calls from one of their own. Of course you will have to hope you get passed onto to someone with technical knowledge. The service clerk you first reach will have no clue as to what you are talking about.

We are a wholesale partner of T-Mobile in the Czech Republic and the deployment of call blocking on forwarded calls has been clearly communicated to us.

Where we have declared OriginatorCallerId as A number instead of OutbondCallerID when forwarding calls, the call is rejected.

As user lightfoot has stated here this is a deliberate blocking and a diversion header is now required for diverted calls.

I can confirm that the reason for the introduction of this regulation and technical requirement is the really high number of spoofed calls.

This is not a mistake, it is not a coincidence, it is a planned change by the network provider who introduced this regulation due to the requirements of the Czech Telecommunications Authority.

 

[Connexium Partner]

I am very curious about this issue. In the meantime, can you maybe reformat the incoming number so the call would not be considered a T-Mobile number? Sort of temporary workaround? (unless I don't understand the issue and this comment do not make sense, then I'm sorry)

 

[laudatio]

I am very curious about this issue. In the meantime, can you maybe reformat the incoming number so the call would not be considered a T-Mobile number? Sort of temporary workaround? (unless I don't understand the issue and this comment do not make sense, then I'm sorry)

Hello, we have set up a fixed hotline number for forwarded calls to mobile, so that mobile users can see the incoming call from our fixed number. In order for the operators to see who is calling them, I have set the SLA time for this queue to 1 second, so the PBX sends them an email where the caller number is visible.

Our distributor recommended us to use the 3cx app for mobile users.

However, we hope 3cx will implement the Diversion Headers feature under pressure from other customers.

 

[Connexium Partner]

Thanks for the update. I think with the v20 on the way, the development team already has a long list of priority tasks to do but it is surely also be a great time to fit this request into their developing map.

But also hope 3cx will consider your request. Although we have had great success with the mobile app in general, here in Canada he have vast distances between population centers. Sometimes mobile network will have "dead-ish" spots while travelling/driving. Phone would still have an LTE connection but its so low that data connections might time out for several minutes. Connection would be just enough for a "mobile" call but not a "data" call. So I hope our government won't get inspired by your laws.

Cheers