You go to switch carriers, swap in the new SIM, and get “No Service.”
“Wait, is it broken?” Right? Yeah, that’s the reaction.
The cause, most of the time, is a SIM lock.
A SIM lock is a “key” on your phone
A SIM lock is a mechanism that restricts a phone to the SIM of the carrier you bought it from.
Put an au SIM into a phone you bought from Docomo, and if it’s locked, it won’t work.
The phone itself isn’t broken. It’s just locked.
Generally no lock today. But older phones need care
Here’s where the story changes a little.
Under revised rules from Japan’s Ministry of Internal Affairs and Communications, phones released on or after October 1, 2021 are generally sold SIM-unlocked.
So with a recent phone, you don’t need to worry much.
Phones released before that date, however, may still be locked.
- You’ve been using a phone you bought several years ago
- You bought it secondhand
- You’re using a hand-me-down from family
If any of these apply to you, check before you switch.
How to check and unlock
1. Check whether the phone is locked
Sometimes you can check from the phone’s settings screen. The sure way is to look at “SIM unlock eligibility” in the My Page of the carrier you’re currently with.
2. If it’s locked, go through the unlock procedure
Most carriers let you do it online through My Page. In a store, a fee may apply, but online it’s often free.
3. Sometimes you can’t unlock it
If you’re still paying off the phone in installments, for example, you may not be able to unlock it until you meet the carrier’s conditions. The conditions differ by carrier, so check the official page.
The “order” of switching matters
The recommended order is this.
- Check whether your phone is SIM-locked with your current carrier
- If it is, unlock it
- Apply to the new carrier (MNP)
If you switch first, you may no longer be able to do the unlock procedure.
Finish the unlock before you switch. Remember just this, and you can avoid getting stuck with no service.
Summary
- A SIM lock is a “key” that ties a phone to a specific carrier
- Phones released on or after October 1, 2021 are generally unlocked
- Older phones and secondhand phones need a lock check
- Finish the unlock before you switch
- Unlock conditions and fees differ by carrier, so check the official page
The biggest waste when switching: scoring a great campaign deal, then burning time because your phone won’t work.
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