Cut your phone bill in half in Japan: How to choose the right data plan for your needs

Quick question: how many GBs did you use last month? If you can't answer in 5 seconds, it's almost certain you're overpaying — because people who don't know their usage usually buy a plan "just to be safe," and "just to be safe" is how carriers make their money. This article teaches you how to measure, match your plan, and make painless cuts to noticeably lighten your bill.

1. Step one: measure your own real numbers

Don't guess — your device has it all recorded:

• iPhone: Settings → Cellular → scroll down to view "Current Period". Note that iPhones don't automatically reset monthly — tap "Reset Statistics" on the first day of your billing cycle, or check more accurately in your carrier's app/account page.
• Android: Settings → Network & internet → SIMs → Data usage — there's a monthly chart showing usage per app.
• Most accurate: Your carrier's account management page — where the exact billing figures are displayed.

Note down the numbers for the past 2–3 months. That is your "shoe size" — now you can go buy shoes.

2. Step two: match your measurements with a plan

Rule of thumb: choose a plan one tier above your actual usage. For example, if you actually use 7GB, buy a 10GB plan, not 20GB. If you happen to run out some month, buying a small top-up data add-on is still cheaper than paying for a giant plan all year round.

3. Cut four classic extra expenses

1. Bundled value-added services: Device insurance, video lockers, waiting tunes… things that are "free for the first 1–2 months" and then silently charge ¥300–1,500/month. Log into your account page, go to registered services (オプション), and cancel everything you don't remember needing.
2. Out-of-plan call charges: Regular calls are billed separately by the minute. Move all casual chatting calls to Zalo/LINE; if your job forces you to make many calls, buying an unlimited 5–10 minutes per call option is usually cheaper than paying per minute.
3. Device insurance for old phones: For a phone you've used for 3 years, the accumulated insurance money could probably buy half a new phone. Consider dropping it and accepting the risk for lower-value devices.
4. "Old-school" plans: Many people still run plans they registered 3–4 years ago, which are more expensive than newer plans with the same data allowance. The Japanese SIM market's prices drop continuously — open the new price list to compare every 6–12 months.

4. The big move: rebalancing between mobile SIM and home WiFi

If you are carrying an unlimited SIM plan of ¥4,000–7,000/month because your housing doesn't have internet, recalculate: home WiFi/fiber optic + small SIM plan is usually cheaper or equal, and the experience is far better (laptops and TVs can be used together). Living with roommates is even better — split a WiFi router among three or four people, and it costs each person only a few hundred to a little over a thousand yen. For details on how to choose, read our article "Internet for Vietnamese families in Japan".

5. Use free WiFi wisely

• Register for the WiFi of chains you frequent (cafes, supermarkets, convenience stores) — register once, and it connects automatically thereafter.
• City libraries, international exchange centers: ample WiFi, ideal study spots for international students.
• However: absolutely do not log into online banking or enter important passwords on unsecured public WiFi. Save sensitive tasks for your personal data — security is worth more than a few MBs.

6. The golden time to switch plans / carriers

1. When your contract lock-in period ends (if any): switching at this time incurs no penalty fees. Check the date in your account page.
2. At the beginning of the billing cycle: many providers charge for a full month if you cancel midway — switching right after the billing cutoff date is most beneficial.
3. When your lifestyle changes: moving to a new place with new WiFi, changing jobs to somewhere closer to home, family members coming over for reunion — every such occasion is a time to re-evaluate your needs.
4. When you see Mobile Number Portability (MNP) promotions: carriers pay quite generous "welcome money" to incoming customers — your number stays the same through a simple MNP procedure.

7. Three 1-minute habits to keep your bill trim

• 1st of every month: glance at last month's data stats — 10 seconds.
• Every quarter: open your account page to review registered services — cut any strange items that popped up.
• Every year: compare your current plan with the latest market price list — if the difference is ¥500/month or more, consider switching.

8. Frequently asked questions

Will I lose purchased data if I switch plans midway?

Depends on the provider: some apply it from the next month (common), others switch immediately and recalculate. Read the terms or ask support directly before hitting switch.

Does unused data at the end of the month roll over to the next month?

Many MVNO plans allow you to roll over unused portions to the following month (kurikoshi) — this is a criterion worth considering when choosing a provider, as it lets you buy a plan close to your exact needs without fearing high and low months.

I'm hesitant to switch because I'm afraid of losing my number, Zalo, or LINE?

Zalo/LINE are tied to your account and won't be lost with the SIM (LINE needs to be backed up before changing your registered number). Your phone number stays the same if you do MNP. This fear causes many people to "grind it out" with an expensive plan for years — don't let it cost you hundreds of thousands of yen.

Conclusion

Saving on your phone bill in Japan doesn't require tricky hacks: measure accurately → buy just enough → cut the excess → review periodically. Today, open your data stats and take a look — if your actual usage isn't even half of what you're paying for, you've just found dropped money. Want someone to calculate it for you? Send HD TELECOM a screenshot of your data stats and current plan name, and we will reply in Vietnamese to tell you if you're overpaying and by how much — completely free, even if you don't buy anything from us.