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Can I use my current SIM card with a SIM-free smartphone or a second-hand smartphone that I have acquired?

You can use it if the system transmission of your current contract and the acquired device match.

However, depending on the combination of the contract and the device, there may be cases it cannot be used. In such cases, you will need to change your contract and SIM card.

For more details tap on the item below that suits your situation.

  • Devices that do not support VoLTE are no longer available due to the termination of the 3G service.

If you are using a 5G SA compatible device with a 5G contract

Although it is possible to use 4G/5G, 5G SA transmission is not available.

To use 5G SA transmission, you need to switch to a 5G SA contract and change your SIM card.

<Procedure>

Procedures must be completed at au Style/au shop. Please note that a handling fee of 3,500 yen (3,850 yen including tax) will be charged for the procedure.

Please have your current SIM card, the device you wish to use, the registered seal and identity verification document  ready when visiting the store.

Click here to check the specific documents (in Japanese only)
  • If you wish to change to eSIM, you can also proceed from here (in Japanese only)

If you are using a 5G SA compatible device with a 4G (VoLTE) contract

You cannot use it. You need to switch to a 5G SA contract and change your SIM card.

<Procedure>

Procedures must be completed at au Style/au shop. Please note that a handling fee of 3,500 yen (3,850 yen including tax) will be charged for the procedure.

Please have your current SIM card, the device you wish to use, the registered seal and identity verification document  ready when visiting the store.

Click here to check the specific documents (in Japanese only)
  • If you wish to change to eSIM, you can also proceed from here. (in Japanese only)

If you are using a 5G compatible device with a 4G (VoLTE) contract

You cannot use it. You will need to switch to a 5G contract (change of plan).

<Procedure>

Procedures must be completed at au Style/au shop. 

  • If you wish to change to 5G/5G SA, a handling fee of 3,500 yen (3,850 yen including tax) will be charged for the procedure.

  • If you wish to change from 4G (VoLTE) to 5G, you can also proceed at the customer center.

    Click here for customer center contact information.

If you are using a 5G/VoLTE compatible device with a 5G SA contract

Operation is not guaranteed. Please switch to a 5G/VoLTE contract and change your SIM card to use it.

<Procedure>

Procedures must be completed at au Style/au shop. Please note that a handling fee of 3,500 yen (3,850 yen including tax) will be charged for the procedure.

Please bring your current SIM card, the device, the registered seal and an identity verification document when visiting the store. 

Click here to check the specific documents (in Japanese only)
  • If you wish to change to eSIM, you can also proceed from here. (in Japanese only)

If you are using a VoLTE compatible device with a 5G contract

You can use it for 4G, but you cannot use 5G transmission.  

If you are using a smartphone with a 4G (VoLTE) mobile phone plan

You cannot use it. However, it will be possible following the procedures below.

For VoLTE/5G compatible smartphones

You need to change to a smartphone plan.

Procedures must be completed at au Style/au shop.

  • If you wish to change to 5G or 5G SA, a fee of 3,500 yen (including tax 3,850 yen) will be charged for the procedure.

  • If you wish to change from 4G (VoLTE) to 5G, you can also proceed at the customer center.

    Click here for customer center contact information.

For 5G SA compatible smartphones

You need to change to a 5G SA contract and change your SIM card.

Procedures must be completed at au Style/au shop.

Please note that a handling fee of 3,500 yen (3,850 yen including tax) will be charged for the procedure.

Please have your current SIM card, the device you wish to use, the registered seal and identity verification document ready when visiting the store.

Click here to check the specific documents (in Japanese only)
  • If you wish to change to eSIM, you can also proceed from here. (in Japanese only)

【Reference】When using another company SIM card

If you wish to use a SIM card from another company in your au mobile phone, it is necessary to unlock the device.

Please refer to the page linked below for details.

For more information on how to unlock your SIM, click here (in Japanese only)

【Reference】When using an another company device

If you wish to use the SIM card in a device of another company, please refer to the page linked below.

For more information on how to proceed, click here (in Japanese only)
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