Request for Call Routing Investigation – Unable to Reach China Unicom +86 156 Numbers

Are you a prepaid or postpaid customer? Were you phone line had proper provision to make international calls? 

As well, Could you make calls to other numbers beside those in China? 

I‘m a Koodo postpaid customer with a perk of 27 countries free long distance call. Samsung S24+

My wife is a Telus postpaid customer with 1000 minutes international long distance call.  Iphone 16 Pro

These two phones works fine to call China Unicom 131 XXXX XXXX.

A friend from China takes a China Unicom 156 XXXX XXXX to Canada, he can call both of us, however,  when we call +86 156 XXXX XXXX, it says ““the number you have dialed is busy now” . 

I asked ChatGPT, and get “Koodo / Telus Call Routing Issue – Trouble Ticket Template” from it.  

ChatGPT says : 

• The +86 156 number is valid, active, and can receive calls from other international carriers.

• The issue appears isolated to the Koodo/Telus network or its upstream routing partners.

• Please escalate to your International Routing / Interconnect team for verification of:

  • Routing tables for +86156

  • Carrier partner configuration

  • SS7/SIP signaling paths

  • Possible blocking or incomplete routing entries

Thanks 

Do you have the appropriate international calling address-ons?

Could you share a screenshot of the ones you currently have on your account?

​@JerryZ 

Are you still encounter this issue?

Just to double check, you are unable to call that number from any of your phone numbers, yours and your wife’s?

If you dial 011 86 156 number, are you getting the same that the number is busy?

This sounds more like that number might not be accepting calls from specific countries.

You’ve already done everything right by confirming the issue is only with +86 156 numbers, and it’s not your account or phone settings. Have you tried calling at different times of day, or from another phone even? 

I dialed 011 86 156 XXXX XXXX with both my phone/Koodo and my wife's phone/Telus, and got "the line is busy now" at 15:50.
However, When I dialed from 156 to Koodo phone and Telus phone, both phone got ring sound after 5 seconds and show the right 156 number.
 

Try both formats when dialing and report back.
•    `+86 156 XXX XXXX`
•    `011 86 156 XXX XXXX`

Eh, are you using the Chinese number in Canada? is that  China Unicom number having proper roaming provision while in Canada?

I tested 2 China Unicom phones roaming to Canada.
131 XXXX XXXX and 156 XXXX XXXX
They can call each other normally.
Koodo and Telus can call 131 XXXX XXXX normally.
Koodo and Telus call 156 XXXX XXXX always "line busy", however 156 XXXX XXXX can call Koodo and Telus normally. 

​@JerryZ 

We recommend scheduling a call back with the technical support for further assistance, as they have access to more advanced tools to further investigate.

You’ll can schedule a callback using the Koodo's Digital Asistant : koodo.com/chat. 

If that happened only to one number, that can be an issue from the phone. From your description, the phone itself might try to block unknown number or its anti-spam system blocked it.

Is the SIM card of the 131 xxx xxxx on the same phone as the 156 xxx xxxx? If not, can you switch SIM and test the 156 xxx xxxx SIM card into the 131 xxx xxxx phone? 

As well, which phone are you using? Is your phone (with the Chinese SIM) in it compatible with Koodo VoLTE network?

Is there more than one SIM loaded on the phone having issues?

I swithed 156 SIM  and 131 SIM, the problem is still unsolved.

Test 1: 156 SIM on a Samsung A56, 131 SIM on a Samsung S10, both connect Telus. 131 SIM works normally. 156 SIM still has above problem.

Test 2: 156 SIM on a Samsung S10, 131 SIM on a Samsung A56, both connect Telus. 131 SIM works normally. 156 SIM still has above problem.

The problem is: 

156 SIM and 131 SIM can call each other.

Koodo/Telus can call 131 SIM each other.

Koodo/Telus call 156 SIM, always “line busy”.

156 SIM can call Koodo/Telus normally.

ChatGPT advice me “This indicates a one-way call failure likely caused by an international routing or carrier partner issue.” 

Since ChatGpt advised you to contact carrier, have you contacted China Unicom to see if they had a block on international incoming call to that number? As well can you check  the "roaming partner" when you put the Chinese SIM in the phone? If possible, try to select another one to see if that can make a difference. 

Since you've already swapped SIMs and confirmed the issue only affects +86 156 numbers, here's a different angle.

Can you test calling the +86 156 number from a non-Telus/Koodo line in Canada, like Rogers, Bell, or Fido? If calls go through on another Canadian carrier, that would confirm it's a Telus/Koodo routing issue, not something on the China Unicom or device side. If you don’t have access to another carrier, maybe ask a friend or use a prepaid SIM for a quick test. The result would give engineers more proof about where the routing is breaking down.

Like Dinh suggested,  have you contacted China Unicom to see if they had a block on international incoming call to that number?