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DTMF and iPhone 6 Plus

I am enjoying my iPhone 6 + but today when I tried to join a conference call, I could not enter the call because the conference bridge wouldn't recognize the DTMF tones. I tried on a second iPone 6 plus and had the same problem. I ended up having to use another phone.


Surely this is a bug. I never had this problem with my iphone 5 on IOS 7.

iPhone 6 Plus, iOS 8

Posted on Sep 22, 2014 7:11 AM

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22 replies

Jul 13, 2015 2:20 PM in response to roadsider

This may work for Verizon, AT&T or T-Mobile that has Volte but Sprint doesn't yet so am assuming "Woodman" doesn't have Sprint as his/her carrier.

I don't think it's carrier specific. iPhone used to send DTMF as long as the button was pushed but now only send DTMF for 2secs max.

Maybe Apple did some tweaking to the Phone App from a DTMF perspective?

Oct 6, 2015 3:28 PM in response to Woodman_2000

I'm using a 6S Plus and transferred carriers to T-Mobile at the same time I got this new phone less than 2 weeks ago. I had this problem with most of the automated phone numbers I called: my DTMF tones weren't received or recognized and I couldn't access those phone numbers. I spoke to several Level 2's at Apple ( four or five of them) and some people at T-Mobile. I also tried this solution of changing LTE from voice and data to voice and restarting the phone. It solved the problem with one phone I call but not all. Today I spoke with a supervisor in Tech at T-Mobile and the problem was traced to my having a low or erratic WiFi signal on my home network as well as having WiFi calling turned on in the settings of the iPhone. Turning off the WiFi settings on the phone raised my bars at home from 1-2 to 2-4. I use a very old Time Capsule as a router and T-Mobile is sending me on loan, a very powerful router which this Tech Supervisor feels will solve the problem here and then I'll be able to turn on WiFi calling on the iPhone again. Not sure why I need that but certainly having a better stronger WiFi network at home is a good thing. As soon as I turned off WiFi calling on the phone settings in addition to having the additional bars on the iPhone I was successfully able to use the DTMF tones to call into the phone numbers I was not able to access before. I have tested it repeatedly now and the problem is entirely fixed. I noticed on researching this that it happened with all the carriers but AT&T which probably does have the strongest signal in my area. And that it happened with iPhones going back to 2010. I hope this solution will help future iPhone owners. It's very hard to pin down but it's a problem apparently caused by the strength of the WiFi signal and might also be related to the actual carrier signal's strength. Something like resetting the iPhone or restoring the iPhone is just busy work that support people put us through when they don't have the answer -- in this case, anyway, because those steps wouldn't help with increasing signals! I'd like to emphasize that the quality of the T-Mobile tech support at the higher levels is certainly superb and it makes a big difference when you can get that quality of help. For this reason I recommend always going higher. Perhaps Apple has just grown bigger than it can comfortably support but the quality of support at Apple isn't what it was, especially disappointing at Level 2. Apple, please try harder. I love you!

Oct 9, 2015 2:43 AM in response to OneEyedGiant

I had this same issue tonight, the IVR I was calling into would not recognize the DTMF tones on my iPhone 6S+, or my wife's iPhone 6. What finally worked for me was also disabling WiFi calling. However, I am using the free T-mobile router that they give out and referenced above by linda36. I have a 105MBPS internet connection, and the ASUS router T-mobile sends is AC. My connection is great, and fast. The issue just seems to be WiFi calling in general.


Anyway, just wanted to drop my two cents. WiFi calling needs to be turned off for your DTMF tones to be recognized, at least that was my experience using T-Mobile iPhones.


FYI for anyone curious, both devices running iOS 9.0.2

Nov 4, 2015 2:15 PM in response to linda36

I experienced the DTMF failure on my iPhone 6S (iOS 9.1) using T-Mobile cellular, and WiFi with a T-Mobile router, and ATT and Netgear routers. It dials OK and people can hear the DtMF tone, but I'm not able to enter numbers into automatic phone answering systems.


My solution was to go to Settings/Cellular and change Enable LTE to Data Only (from Voice & Data). No reboot was necessary. It has its limitations, but it works for now.

Nov 24, 2015 5:53 PM in response to jkbales

Hello! I had the same issue. I called T-Mobile and they figured out what was wrong. I already had Cellular > Enable LTE > Data Only. I also had to turn off my WiFi Calling (Settings > Wi-Fi Calling > OFF) and that seemed to do the trick. Guess I'll just need to turn that feature off and on when I'm calling an IVR system! Glad to have it working again, this was getting frustrating! Hope this helps others.

Dec 2, 2015 8:42 AM in response to OneEyedGiant

I was having a similar issue with DTMF tones not being recognized by my community's call box in order to open the gate. Whenever someone called to get in (lawn guy, delivery, etc) I couldn't get the gate to open for them. After trying everything I had read and different combinations of "fixes" I had found on a lot of other posts, I seem to have come across a solution that worked for my situation.


**My network is AT&T so this may not apply to everyone with a similar issue.

- Settings>Cellular>Enable LTE>Data Only

- Turn off Wi-Fi

- Turn off Bluetooth

- Turn off Personal Hotspot


This means I'll either have to run with all these things off all the time or have people call me twice so I can make the systemic changes between calls and let them in on the second call. It's not ideal but it seems to work (so far).


Hope this helps anyone with a similar issue that isn't getting anywhere with tech support.

DTMF and iPhone 6 Plus

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