WhatsApp for Samsung Galaxy Note 4 Duos

First clean the earpiece grille with a soft brush, since dust buildup is a common cause on aging Note 4 units. Then test in Safe Mode (press and hold Power, then long-press 'Power off' until 'Safe mode' appears) to rule out a third-party app, and toggle Bluetooth off in case audio is being routed to a paired device. If it only happens on some calls, clear the Phone app's cache under Settings > Application manager > Phone > Storage > Clear cache. See how others solved this on Reddit

It can still handle calls, messaging, a browser and light apps, but it's stuck on an old Android version with no security patches, so avoid banking apps and keep it for secondary use. To squeeze out more speed, go to Settings > Application manager, disable bloatware you never open, then in Settings > Developer options reduce the window and transition animation scales. Expect some newer Play Store apps to refuse to install, since they require a higher Android version. See how others solved this on Reddit

Free up internal storage first (Settings > Storage), since the device slows badly once it nears full; move photos to a microSD card or back them up to Google Photos and delete the local copies. Then wipe the cache partition by powering off and holding Volume Up + Home + Power, then selecting 'wipe cache partition' in recovery. As a last resort, a factory reset under Settings > Backup and reset > Factory data reset restores near-original responsiveness after years of buildup. See how others solved this on Reddit

The Note 4 has a removable battery, so the simplest fix after this many years is to swap in a fresh OEM-spec battery rather than fighting software settings. In the meantime, open Settings > Battery to spot rogue apps, enable Power saving mode, and turn off background sync for accounts you rarely use under Settings > Accounts. Lowering screen brightness and shortening the screen timeout under Settings > Display also stretches each charge noticeably. See how others solved this on Reddit

Many modern apps have dropped support for the Note 4's old Android version, so the Play Store will show them as incompatible or stop pushing updates. Clear the Play Store cache (Settings > Application manager > Google Play Store > Storage > Clear cache) and the Google Play services cache to fix download errors, then keep using the older, still-working versions you already have installed. For apps that simply won't run anymore, switch to lightweight 'Go' or 'Lite' alternatives that target older hardware. See how others solved this on Reddit

Since the Note 4 stopped receiving Android security patches years ago, treat it as not safe for sensitive logins like banking and primary email. If you must, use it only on trusted Wi-Fi, keep Google Play Protect enabled (open the Play Store, tap your profile/menu, then Play Protect), and avoid sideloading APKs from unknown sites. For anything financial, use a newer device and keep the Note 4 for music, alarms, browsing and calls. See how others solved this on Reddit