Unicom card has opened the international roaming service. In Japan, you can receive phone calls and text messages, and you can open 4g traffic, but you can't make phone calls and send text messages.

1, need to confirm whether the mobile phone number has international roaming rights. The knowledge in this respect is as follows: Unicom's post-paid or pre-paid mobile phone numbers support the international roaming function, and the post-paid mobile phone numbers turn off the international roaming authority by default, so you need to contact Unicom's customer service or apply to Unicom's business hall to open the international roaming authority, and then use it abroad; Unicom's prepaid mobile phone number has the right of international roaming by default, so it can be used abroad without application. The status quo of prepaid international roaming countries is different from that of post-payment, and there are fewer countries. Prepaid customers need to ensure that their accounts have sufficient balance when using abroad.

2. After the international roaming authority is enabled for the mobile phone number, the dialing method for you to call back domestic calls abroad is: +86 mobile phone number or +86 long-distance area code and fixed-line number (the long-distance area code should be 0, such as10 in Beijing);

3. After the mobile phone number roams abroad, the format of sending SMS to the domestic mobile phone number is: directly input the other party's 1 1 cell phone number;

Please check whether the format of calling and sending SMS is correct. If it still doesn't work normally, you can contact China Unicom's international roaming service hotline:+8618618610010, and use China Unicom's mobile phone to dial the hotline overseas and enjoy free service.