WhatsApp for Samsung Galaxy S Relay 4G T699

In practice, no. The T699 is an LTE-era handset that relied on T-Mobile's HSPA+/3G for voice and lacks VoLTE, and T-Mobile retired its 3G/UMTS network in 2022 and now requires VoLTE for calls. Without VoLTE the phone can't reliably place calls or texts on the current network even where LTE data exists. There is no setting or update that adds VoLTE or re-enables the T699, so an active line needs a newer VoLTE-capable phone. See how others solved this on Reddit

Unlocking only removes the carrier lock; it can't add the modern LTE bands and VoLTE that US carriers now require, so even an unlocked T699 won't get reliable service on T-Mobile, AT&T, or their MVNOs. To request the unlock you contact T-Mobile (or use the carrier's unlock request, not a menu in Settings > About phone), but it won't restore voice service on a phone this old. It's best treated as a backup or offline device rather than an active line. See how others solved this on Reddit

The T699 shipped on an old Android build (Ice Cream Sandwich/Jelly Bean) that predates the modern carrier Wi-Fi Calling toggle, so there's no working Wi-Fi Calling switch under Settings even though the phone has Wi-Fi. You can still use Wi-Fi for a browser or an over-the-top messaging app like a VoIP service, but it can't route your carrier number over Wi-Fi. Real Wi-Fi Calling requires a newer Samsung, where it lives under Settings > Connections > Wi-Fi Calling. See how others solved this on Reddit

Since the T699 can't do VoLTE, owners who want that hardware-keyboard feel usually move to newer QWERTY-slider or keyboard-case devices that support T-Mobile's LTE bands and VoLTE. Check any replacement's band and VoLTE compatibility on T-Mobile's IMEI/device checker before buying, since a keyboard alone doesn't guarantee it will activate. The Relay itself can stay useful purely over Wi-Fi for note-taking or as a small media device. See how others solved this on Reddit

Yes. With no cellular service the T699 still works as an offline Android device over Wi-Fi for music, photos, and stored apps. Load files via USB to its internal storage or a microSD card, play them with a media app, and use Settings > Wi-Fi to get online for downloads. Leaving the SIM out also helps battery life, since it stops the phone constantly searching for a network it can no longer use. See how others solved this on Reddit