Go to Settings → Connections → Mobile Networks → Network Mode. If you (or someone else) set this to “3G only” or “2G/3G auto,” your phone will never use 4G. Change it to “LTE/3G/2G (auto connect)” to fix this.

So the real question is usually: “Is my A51 currently using 4G, or is it stuck on 3G?” Here’s how to check.

There are two main versions of this phone. You can distinguish them by their internal hardware or model number: : Uses the Exynos 9611 chipset.

: Tap on Network mode . If you see options like LTE/3G/2G (auto connect) , your device is 4G capable. Identifying Your Model (4G vs. 5G)

| Question | Answer | |----------|--------| | Is Galaxy A51 a 3G phone? | ❌ No | | Is Galaxy A51 a 4G phone? | ✅ Yes | | Can it connect to 3G networks? | ✅ Yes (fallback only) | | Should I replace it if 3G is shutting down? | ❌ No, it will still use 4G |

: Uses the Exynos 980 chipset and explicitly includes "5G" in its name and settings. External Verification Methods If you cannot access the phone's menu, use these methods: Samsung Galaxy A51 - Full phone specifications

If the field says “UMTS” or “HSPA,” do not panic. That is your current connection, not your phone’s maximum capability. Look for the “LTE” mention elsewhere in the menu.