Could switching from a major carrier cut your phone bill by around JPY 5,000 a month?

Could the difference really be around JPY 5,000? A published-rate example

As recorded on October 23, 2026, docomo MAX’s pre-discount base charge for more than 3GB through unlimited use was JPY 8,448 a month, versus JPY 2,970 for ahamo’s then-current 30GB plan. The tax-inclusive base-charge difference was 8,448 − 2,970 = JPY 5,478, an example of roughly JPY 5,000 a month.

Source: docomo MAX official terms and fee table

Source: ahamo official prices and data allowances

This compares unlimited data with 30GB and different benefits and support. The difference does not apply unchanged to customers with bundle or family discounts, or those using more than 30GB. Treat it as a starting point for people whose usual use fits 30GB and who do not need the extras.

Important: ahamo has announced a December 2026 change

The cited official announcement scheduled a tiered ahamo plan from December 1, 2026: 40GB at JPY 3,135 through 120GB at JPY 5,115 a month. Do not project the then-current 30GB / JPY 2,970 charge into future annual savings.

Source: ahamo official change announcement

Source: docomo announcement of plan and monthly-fee revisions

Check the rates applying on your application date and throughout your intended use. The JPY 5,478 difference is a dated comparison, not a guarantee after revisions. Recheck both plans’ revisions and discount conditions.

Check three months of data use before leaving a large-data plan

Check three months of data and call time, including the busiest month. Home Wi-Fi may make a smaller allowance practical; frequent video, tethering or business travel may lead to extra data purchases.

Online-only plans assume online procedures. For sub-brands, compare shop support and bundle conditions; for lower-cost SIMs, consider busy-hour performance too. Narrow choices by coverage where you live, lunchtime use and support, rather than price rankings alone.

Costs beyond the base charge can change the difference

The cited ahamo rate includes domestic calls up to five minutes each; longer calls cost JPY 22 per 30 seconds, while SMS and some numbers cost extra. Add any needed calling option before comparing totals.

Source: ahamo domestic-call and pricing notes

Changing networks does not erase device instalments. Check return deadlines and damage conditions for any device-return programme. Separate device and protection payments from communication charges on your current bill.

List lost broadband or family discounts, rewards and video services. Add the cost if you will buy replacement services separately. Consider the change for the whole family, not just your line.

Check email, device compatibility and support before signing up

If you use carrier email, check portability eligibility, fees and deadlines. Review addresses registered with banks, shops and authentication services, changing them before switching if necessary. For docomo-to-ahamo changes, check email-portability application timing.

Source: ahamo official application process

Check the supported-device list, frequency bands, SIM lock and eSIM support. Seller and model numbers can matter even with the same product name. For eSIM, review activation steps and arrange Wi-Fi for setup.

If online procedures concern you, check what shop support covers and costs. Congestion and speed depend on place and time; cheaper plans do not guarantee identical performance everywhere.

Number portability differs from a same-company plan change

Use MNP to retain your number when changing companies. Follow the receiving provider’s instructions for one-stop support or reservation numbers. Do not cancel your old line first if you want to retain the number.

The docomo MAX-to-ahamo example is a plan change within docomo, not an MNP transfer to another company. The cited official FAQ states no cancellation or administration fee for that change; it does not mean all inter-company transfers are free.

Source: ahamo official FAQ on changing from docomo

Cancellation charges, initial fees, prorating and SIM fees vary with contract terms and timing. Check early-cancellation conditions too. Keep temporary reward offers separate from recurring monthly base charges.

Calculate your own difference with this formula

Compare “current service + necessary options − actual discounts” with “new service + necessary options − new discounts.” Include continuing device payments on both sides, and note lost family discounts, replacement services and one-off costs separately.

Not everyone will save JPY 5,000. Existing low-data budget plans may offer little room to cut, while some people need larger allowances or support. Start by opening your bill and checking unused capacity and services.