Supported devices: what makes a phone work well (or badly) for internet calls

Phones and numbers · Published 2026-10-24

"Supported devices" lists exist for a reason. Whether an internet call rings reliably, sounds clear and survives the screen turning off depends on the operating system, the manufacturer's battery rules, carrier configuration and the accessories you use.

Operating system versions

Calling apps support a range of operating system versions and drop older ones over time, because they depend on security updates and on system frameworks that change. When a phone stops receiving operating system updates, its apps eventually stop being updated too. Before relying on a phone for calls, check two things: the minimum iOS or Android version the app requires (listed on its App Store or Google Play page), and whether the manufacturer still provides security updates for the device.

Why incoming calls sometimes fail to ring

A traditional call wakes the phone through the mobile network. An app call has to wake the app, which the operating system may be keeping asleep to save battery. iOS and Android solve this differently.

iPhone: CallKit and VoIP push

Apple provides two frameworks for calling apps. CallKit lets an app present incoming calls on the native call screen, including on the lock screen, and integrate with the Phone app's recents, Bluetooth and CarPlay. PushKit delivers special "VoIP push" notifications that wake the app for an incoming call. Since iOS 13, apps must report every VoIP push to CallKit as an incoming call; the system penalises apps that do not. For users this means app calls on a current iPhone generally ring like normal calls, provided notifications for the app are allowed.

Android: Telecom framework, high-priority messages and battery savers

Android's Telecom framework lets calling apps integrate with the system call interface and audio routing. Since Android 6.0, Doze mode restricts background activity when the phone is idle (Android documentation on Doze and App Standby); calling apps use high-priority push messages to wake up for calls. On top of that, several manufacturers add their own, more aggressive battery management. If calls only ring when you open the app:

• Set the app's battery usage to "unrestricted" or exclude it from battery optimisation.
• Allow notifications, including on the lock screen, and the "display over other apps" or full-screen notification permission if the app requests it.
• Check that data saver modes are not blocking background data for the app.

Carrier features: VoLTE and Wi-Fi calling

Carrier calling features work differently from apps. VoLTE and Wi-Fi calling depend on configuration files that tell the phone how to talk to a particular operator's IMS network. Those settings ship with the phone's software, are often operator-specific, and must be validated by the operator. That is why:

• A phone imported from another country may support Wi-Fi calling in general but not on your operator.
• Budget and prepaid brands that share a larger operator's network may not enable features the parent operator offers.
• A software update can suddenly add, or occasionally remove, Wi-Fi calling for your network.

Operators publish lists of handsets on which they enable VoLTE and Wi-Fi calling. As older 2G and 3G networks are switched off in many countries, a phone that cannot use VoLTE on your network may be unable to make ordinary calls at all, so this list is worth checking before buying a second-hand or imported phone.

Bluetooth headsets and car kits

Call audio over Bluetooth has historically used the Hands-Free Profile (HFP), which is designed for two-way voice. Early versions carried narrowband audio; HFP 1.6 added wideband speech with the mSBC codec, and later versions add better codecs (Bluetooth specifications). The newer LE Audio standard uses the LC3 codec for both music and calls. In practice:

• Headphones that sound excellent for music can sound flat on calls, because the call path uses a different profile and codec.
• Both the phone and the headset must support wideband speech for HD-quality calls over Bluetooth.
• If the other person hears you poorly, test with the phone's own microphone: built-in microphones are often better than those in small earbuds, especially in wind.

Tablets, computers and watches

• Tablets without a mobile plan can make app calls over Wi-Fi. Many operators also let tablets and computers make and receive calls on your phone number through linked-device features; support varies by operator and platform.
• Desktop apps and browsers often use WebRTC, which works in current versions of the major browsers without plugins. Grant microphone permission to the site or app, and use a headset to avoid echo.
• Smartwatches with eSIM can take calls on your number away from the phone if your operator supports the watch's number-sharing service.

Microphone and permission issues

One-way audio is often caused by permissions rather than networks. Both iOS and Android require explicit permission for an app to use the microphone, and Android can automatically revoke permissions from apps that have not been used for months. If people cannot hear you, check the app's microphone permission first, then see the network-related causes in our call quality guide.

Checklist before relying on a phone for calls

1. Is the operating system still supported, and does the app support that version?
2. Do incoming app calls ring with the screen off and the app closed?
3. Is the phone on your operator's VoLTE and Wi-Fi calling list?
4. Is the phone unlocked, if you plan to use local SIMs or eSIMs abroad?
5. Have you tested your headset on an actual call, not just with music?