What happens if I pick Always Ask instead of a fixed SIM?

Every time you place a call, a small prompt appears letting you tap SIM1 or SIM2 before the call connects. This is useful if you regularly switch lines but adds one extra tap per call.

Why is the Calling option missing from my SIM settings?

The option only appears when two SIM cards are inserted and both are active. With a single SIM inserted, ColorOS skips the selection screen entirely since there is nothing to choose between.

Can data still use a different SIM than the one I set for calls?

Yes. Mobile data has its own default SIM, set independently under Settings ➔ SIM card & mobile data ➔ Mobile Data. Changing the calling preference does not affect it.

Oppo

Oppo: Set Default SIM Card for Outgoing Calls

With two SIM cards active on your Oppo phone, the system decides on its own which SIM handles an outgoing call unless you set a fixed one. If calls keep going out on the wrong SIM, or ColorOS asks you every single time which line to use, the calling preference in your dual-SIM settings is the setting responsible.

Updated: 04.08.20263 min4 steps

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Oppo

Set Default SIM Card for Calls auf Oppo

On an Oppo phone with two active SIM cards, calls do not automatically use the SIM you expect. ColorOS applies a separate calling preference that overrides whichever SIM handled your last call or app action.

This preference sits inside the dual-SIM management screen and controls only voice calls. Data usage and SMS routing follow their own settings and are not changed by this fix.

To set it, go to Settings ➔ SIM card & mobile data ➔ Calling and choose SIM1, SIM2 or Always Ask.

Picking a fixed SIM makes every outgoing call use that line by default, even from the dialer or contacts app. Choosing Always Ask brings up a selection dialog before each call, which helps if you switch lines often for cost or coverage reasons.

If calls still leave on the wrong SIM after this change, check whether one SIM slot has no signal or is set to airplane-style restriction, since a missing signal can force calls onto the other line regardless of this preference.

Frequently asked questions

No. Calls and SMS use separate defaults in ColorOS. Go to Settings ➔ SIM card & mobile data and check the Messaging section separately if texts go out on the wrong SIM.

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Network & Connectivity

Oppo: Set Default SIM Card for Outgoing Calls

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Set Default SIM Card for Calls auf Oppo

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