DTMF response fails on forwarded call to mobile phone

[flexserve]

v15.5, external call forwarding to mobile phone with bounce back. Answer phone (Galaxy S8 Active), listen to call announcement, press 1, nothing happens/call on cell ends, caller forwarded to voicemail as if no one answered. Same phone, dial in to 3CX, can navigate and dial extension no problems. Issue is only on external call forward to mobile number/ring back.

I have this issue on two different systems, same patch level, one cloud hosted on Debian, one onsite on Windows 8.1; cloud is Pro, onsite is Standard.

This is calling the phone directly, not ringing the 3CX Android app.

 

[cobaltit]

Thanks for reporting the problem. Was there a question somewhere?

 

[flexserve]

Yes, please excuse me for not stating the obvious. Has anyone else run into this problem and/or have a suggestion that might correct the issue?

 

[cobaltit]

So yes lots of people run into this issue. You didn't mention what dial tone you are using but since you have the same experience across two systems I'm going to assume they are using the same unsupported SIP provider. You'll want to wireshark a call that works and call that doesn't to compare but since 3CX doesn't have any means of changing the DTMF method it's going to depend on your provider.

https://www.3cx.com/blog/voip-howto/dtmf-rfc2833/

No one has reported a problem on our system but I don't know too many that do rebound. I'll test on our trunks to confirm it's not something in 3CX.

Also, are you on SP6 because it also wasn't mentioned in your post

 

[cobaltit]

Ok just tested it on my system and it works fine which is good considering we just applied for trunk certification. This scenario isn't actually covered on the interop testing although if you pass all the other ones it should be fine. Do you only have one trunk for calls in/out of the system?

 

[YiannisH_3CX]

Hello @flexserve

As @cobaltit mentioned you will need to use wireshark to be able to troubleshoot the issue as it sounds like DTMF tones are not being received by the system. You could also try a test trunk from a different provider to see if you are experiencing the same issue

 

[flexserve]

1. SIP provider IS supported
2. Yes, SP6 both platforms
3. Have other trunks available will test through one of them.

 

[YiannisH_3CX]

Can you share who the provider is so we can try and replicate the scenario? Let us know of the results of the test.

 

[flexserve]

1. Siptrunk.com
2. What is unique is that the issue is only on call forwarding response w/DTMF (system fails to respond to pressing "1" to accept call); same phone , if I dial into the system, system responds to DTMF from phone, dial extension or IVR.

 

[YiannisH_3CX]

I replicated your scenario and it works for me. I was able to accept the call after it was forwarded out so that could mean that in your case the upstream provider is not sending the DTMF tone to Siptrunk.com. One thing to check is that the options "Supports Re-Invite" and "Support Replaces" are not enabled under the trunk options.