TL; DR
- OPPO and OnePlus (ColorOS and OxygenOS) have a feature called Backup Calling that helps users make a call even when there is no signal.
- If SIM1 has no network, it uses the mobile data of SIM2 to mimic Wi-Fi calling and make the call possible.
You know that moment in an elevator when you need to make a call, but your SIM just dies on you? Turns out, OnePlus and OPPO have already solved this problem—with a feature that’s been around for a while but no one’s really talking about: Backup Calling.
This feature, also found on the OnePlus 13 (review), OPPO Find X8 (review), Find X8 Pro (review), and a few other phones, is a lifesaver for dual-SIM users. Imagine SIM1 is your default calling SIM but has zero network. Normally, you’d have no choice but to wait for the signal.
But with Backup Calling, if SIM2 has mobile data, your phone uses it to route the call for SIM1, like it’s tricking your phone into thinking it’s on Wi-Fi. This allows the SIM1 to make calls via Wi-Fi calling without a signal.
ALSO READ: OnePlus 13R vs. iQOO 12: Which Snapdragon 8 Gen 3 Smartphone Is Better For You?
Yes, this has been on OnePlus phones for quite a while now. Weirdly enough, nobody has made a fuss about it. But it’s the kind of feature you don’t know you need until you’re stuck in an elevator or a basement, wishing you had signal.
How to enable
Unfortunately, even OnePlus or OPPO don’t advertise it enough. Add to that, it’s disabled by default. However, activating it takes a few simple taps:
1. Settings > Mobile Network > tap your SIM Card.
2. Then, tap Wi-Fi Calling and then turn on Backup Calling.
Make sure to do this for both the SIM cards.
ALSO READ: OnePlus 13R Review: Is OxygenOS Losing Its Charm?
Keep it turned on, and you’re always ready. No SIM swapping, no missed calls.
It’s 2025, and dual-SIM setups are everywhere. Work SIM, personal SIM, or even local SIMs while traveling—this feature just makes sense. OPPO and OnePlus have made it available, and it’s time for the rest of the industry to catch up.
So, here’s the takeaway: if you’ve got dual SIMs and one of these phones that support Backup Calling, this feature is super useful, and you should enable it right away. And if you’re a smartphone brand, it’s time to copy this.
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