# Allow Cellular Data Switching on iPhone: How It Works URL: https://byshahid.com/blog/allow-cellular-data-switching-iphone/ App: Secret Codes: IMEI & Carrier (https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322) Author: Muhammad Shahid Updated: 2026-11-04 > Let a dual SIM iPhone borrow the other line's data when coverage is better. On a dual SIM iPhone one line is the designated data line. Allow Cellular Data Switching lets iOS temporarily use the other line for data when that gives better coverage or availability. It matters for calls, not just browsing. - **What it does:** Let a dual SIM iPhone borrow the other line's data when coverage is better. - **Published for:** any iPhone, Verizon, AT&T, T-Mobile and UScellular - **Type:** iOS setting Let a dual SIM iPhone borrow the other line's data when coverage is better. This page explains what it does, how to use it on an iPhone and which carriers it applies to. I build **Secret Codes: IMEI & Carrier**, a free iPhone app with 317 checked codes and guides, including this one. If you would rather tap than memorise, [get Secret Codes on the App Store](https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322). ## What is Allow Cellular Data Switching? On a dual SIM iPhone one line is the designated data line. Allow Cellular Data Switching lets iOS temporarily use the other line for data when that gives better coverage or availability. It matters for calls, not just browsing. Apple documents that if a call arrives on one line while the other is busy and there is no Wi-Fi, the iPhone uses the data of the line already in use to deliver the second call. For that to work, the busy line must be permitted to use data, either as the default line or as the non default line with this switch on. The cost is that data may be used on the line you did not intend, and if Data Roaming is on and you are outside that carrier's home area, roaming charges can follow. **Important:** Data used on the secondary line is billed by that carrier, and combining this with Data Roaming abroad is a common source of unexpected charges. ## How do I do it? - Open the Settings app. - Tap Cellular. - Tap Cellular Data and choose your default data line. - Turn on Allow Cellular Data Switching. ## Which carriers does this apply to? | Published for | any iPhone, Verizon, AT&T, T-Mobile and UScellular | | Type | iOS setting | | Good to know | Dual SIM iPhones only: one physical SIM plus eSIM on iPhone XR, XS, SE (2nd generation) and later, or two eSIMs on iPhone 13, iPhone SE (3rd generation) and later. | _Screenshot: The Secret Codes detail screen shows the steps, the carriers and an Open in Phone button._ ## Related iphone phone and message settings - [Allow More Data On 5G](/blog/allow-more-data-on-5g-iphone/) - [Flash For Alerts](/blog/flash-for-alerts-iphone/) - [5G Standalone And Voice Over 5G SA](/blog/5g-standalone-and-voice-over-5g-sa-iphone/) - [Hearing Devices And Hearing Aid Compatibility](/blog/hearing-devices-and-hearing-aid-compatibility-iphone/) - [Cellular Data Network And APN](/blog/cellular-data-network-and-apn-iphone/) - [Live Captions On Calls](/blog/live-captions-on-calls-iphone/) See all [iphone phone and message settings](/blog/iphone-codes/phone-settings/) or [every category of iPhone codes](/blog/iphone-codes/). ## How Secret Codes helps Secret Codes keeps this and every other entry a search away. Pick your carrier once and each entry says whether it is published for your line. You can save favourites, add a private note, and record whether a code worked on your line. This entry is part of Secret Codes Pro. **Secret Codes: IMEI & Carrier** is free on the App Store: https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322 ## FAQ ### What is Allow Cellular Data Switching on iPhone? Let a dual SIM iPhone borrow the other line's data when coverage is better. On a dual SIM iPhone one line is the designated data line. Allow Cellular Data Switching lets iOS temporarily use the other line for data when that gives better coverage or availability. ### What else should I know about Allow Cellular Data Switching? It matters for calls, not just browsing. Apple documents that if a call arrives on one line while the other is busy and there is no Wi-Fi, the iPhone uses the data of the line already in use to deliver the second call. ### What are the steps for Allow Cellular Data Switching? 1. Open the Settings app. 2. Tap Cellular. 3. Tap Cellular Data and choose your default data line. 4. Turn on Allow Cellular Data Switching. ### Where do I find Allow Cellular Data Switching? In the Settings app on your iPhone. ### Is there a dial code for Allow Cellular Data Switching? No. On iPhone this is not a dial code, so you use the steps on this page instead. ### Which carriers does Allow Cellular Data Switching work on? It is published for any iPhone, Verizon, AT&T, T-Mobile and UScellular. Dual SIM iPhones only: one physical SIM plus eSIM on iPhone XR, XS, SE (2nd generation) and later, or two eSIMs on iPhone 13, iPhone SE (3rd generation) and later. ### Is there anything to watch out for with Allow Cellular Data Switching? Data used on the secondary line is billed by that carrier, and combining this with Data Roaming abroad is a common source of unexpected charges. ### Does Allow Cellular Data Switching work on Android phones too? These steps are for iPhone. Android phones have their own menus. ### Will Allow Cellular Data Switching work outside the US? The iPhone steps stay the same, although some features depend on your carrier and region. ### What if Allow Cellular Data Switching does not work on my iPhone? Check that it applies to your carrier first, because carriers decide which services they offer and can change them. If it should apply to your line, contact your carrier. ### What is related to Allow Cellular Data Switching? Allow More Data On 5G. Unlock higher quality FaceTime, iOS updates and iCloud backups over cellular. ### What else is in this category? Flash For Alerts. Blink the camera LED, the screen, or both when a call comes in. ## Sources - [Apple Support: iPhone User Guide](https://support.apple.com/guide/iphone/welcome/ios)