Recharging b-mobile data SIM

One month ago, I've activated a b-mobile SIM for mobile data in Japan. Since the initial charge is only valid for 30 days, now is the time that I need to recharge the SIM for another month. It's not as straightforward as I've expected it to be, so I'm writing this post to share my experience with anyone else who may be in the same position as I am.

The 2 options provided by b-mobile are auto-charge and manual charge. However, they are not created equal. For the 1 GB SIM, manual charge only allows for the more expensive 1 GB valid for 120 days (¥8,350), while auto-charge allows you to select between 30 days (¥3,100) and 120 days validity!

Manual charge should be straight-forward, but obviously I'd want the cheaper package since I'll only spend one more month here (and 1 GB per 3 months is not enough for me), so I'll have to enable auto-charge.

The bCharge app (as seen in the screenshot above) states that auto charge will take place 5 days before the expiration date or when your balance approaches zero, while the website states that auto charge will take place 2 days before expiry. The truth is... neither of that.

Auto-charge will take place at midnight (Japan time) and deducts the money from your credit/debit card, however, it will not take effect right away but instead becomes a "Charge Credit" in your account. The charge credit will take place when your balance reaches zero or you've reached your expiration date.

I haven't tested this, but b-mobile's website states that if you use auto-charge while your SIM is expired (within 10 days), the auto-charge will take place right away and you can continue using your data without having to wait until midnight.

And don't forget to turn off auto-charge after you've recharged, otherwise you'll be continue to be charged the next month even after you've left Japan!