Why iPhone Keypad Presses (DTMF Tones) Don't Always Work During Calls — What You Should Know
Why iPhone Keypad Presses (DTMF Tones) Don't Always Work During Calls — What You Should Know
If you've ever tried to access your voicemail or navigate an auto attendant system from your iPhone and found that the number keys just don’t seem to work—you're not alone. This is a known issue that has persisted across multiple iOS versions, and it's causing headaches for users and IT providers alike.
What Are DTMF Tones?
DTMF stands for Dual-Tone Multi-Frequency. These are the tones your phone generates when you press a number on the keypad during a call. Each number produces a unique combination of two tones that systems like voicemail, phone menus, and auto attendants use to understand your input. For example, when you “Press 1 for Sales,” that tone is how the system knows what button you pressed.
What’s the Problem?
When calling into systems that require DTMF (Dual Tone Multi-Frequency) signals—like voicemail menus, automated attendants, or conference bridges—you may notice that pressing the keys doesn’t register as expected. You might press “1” and hear nothing, or the system simply doesn’t respond.
While it might seem like an issue with the phone system or voicemail provider, extensive testing has shown otherwise. Calls placed from Android devices, landlines, and even older iPhones don’t experience the same problem. The issue appears to specifically affect iPhones running newer versions of iOS—starting notably with iOS 13 and continuing in some form even today.
Where the Issue Really Lies
The root of the problem isn't your voicemail system—it’s how the iPhone and mobile carriers handle DTMF tones over modern cellular networks.
Today’s cellular networks use VoLTE (Voice over LTE) technology, which is similar to VoIP (Voice over IP). In a VoLTE call, your voice—and crucially, your keypresses—are converted into data packets and transmitted over an IP-based data network. Unlike older networks where the device would emit the actual audible DTMF tone, VoLTE instructs the carrier to generate and relay the tone on its behalf.
If that chain breaks—whether in the iPhone, the mobile carrier, or the handoff to the land-based carrier—your keypresses may never reach the receiving system.
To make matters more complicated, there are often two carriers involved in each call: the mobile carrier (like AT&T, Verizon, or T-Mobile), and the landline carrier on the other end (such as Cox or another VoIP provider). Both carriers need to correctly interpret and relay the DTMF signals, or the tones simply won’t work.
What We’ve Seen
In our testing, calls placed from iPhones frequently fail to register keypresses on voicemail and auto attendant systems, especially when Cox is the receiving carrier. Since Cox is a major provider in our area, this is the most common scenario we encounter.
Importantly, this is not a problem with your phone system or voicemail. Our team has confirmed this by successfully placing calls from various other devices and carriers. This is a device and network issue, and unfortunately, not something we can fix on the system side.
Community Feedback and Workarounds
The issue is well documented in Apple’s own forums, including this thread with years of discussion: Apple Support Thread. Some users have reported that enabling speakerphone before dialing keypresses may help, although results vary. Others say the issue was resolved for them in iOS 14 or by switching mobile carriers.
But because the issue often depends on a combination of device software and network compatibility, results will differ from user to user—and even call to call.
What You Can Do
If you're experiencing this issue:
Try turning on speakerphone before entering keypresses.
Update your iPhone to the latest version of iOS.
If the issue persists, try placing the same call from a landline or Android device.
Consider reaching out to your mobile carrier to report the issue. They may be able to adjust settings on your account or escalate to their network engineers.
Final Thoughts
While frustrating, this DTMF issue is not uncommon and unfortunately sits outside the control of your phone system provider. We recommend sharing this information with anyone in your organization experiencing difficulties navigating voicemail or automated phone systems from their iPhone.
If you have questions or need help troubleshooting other aspects of your communication system, we're always here to support you. Contact Us
