O2's 30-day option is £9. A Slashtel eSIM with at least 1GB for the same trip is £3.51. Keep your O2 number for calls and texts.
Buy the Japan eSIM →O2's 30-day Data Roaming Bolt On Zone 2 (1GB) option costs £9 (1GB of data). A Slashtel data eSIM for Japan with at least 1GB for 30 days costs $4.69, about £3.51, so £5.49 less. The eSIM is data only: keep your UK SIM in the phone for calls and texts. O2 prices checked on o2.co.uk on 26 October 2026.
| O2 | Includes | Slashtel eSIM (same days or more) | Difference |
|---|---|---|---|
| £21 · 3 days£7/day x 3 days | £7/day x 3 days | 3GB, 15 days: $3.89 (≈£2.91) | £18.09 less |
| £35 · 5 days£7/day x 5 days | £7/day x 5 days | 5GB, 30 days: $5.39 (≈£4.03) | £30.97 less |
| £49 · 7 days£7/day x 7 days | £7/day x 7 days | 10GB, 30 days: $9.39 (≈£7.02) | £41.98 less |
| £70 · 10 days£7/day x 10 days | £7/day x 10 days | 10GB, 30 days: $9.39 (≈£7.02) | £62.98 less |
| £9 · 30 days | 1GB data only | 3GB, 30 days: $4.69 (≈£3.51) | £5.49 less |
O2 prices from o2.co.uk, checked 26 October 2026; O2's options include calls as well as data. Where O2 charges by the day, we compare an eSIM with at least 1GB a day. Europe Zone (incl. Switzerland, Ireland, Austria, Poland, Czech Republic, Hungary) is included on all O2 tariffs up to a 25GB roaming limit; Turkey is not in the Europe Zone. The O2 Travel Bolt On covers the 75 Zone 1 and 2 destinations (USA, Canada, Australia, UAE, Thailand, Japan, India and more) at £7 a day. Zone 3 (120 destinations incl. South Korea, Vietnam, Philippines, Maldives, Taiwan, Nep Slashtel prices are live, in US dollars, converted at 0.75 per $1 (daily reference rate); your card is charged in your own currency at checkout. O2 is a trademark of Telefonica UK Limited (Virgin Media O2). Slashtel is not affiliated with O2.
Yes, O2 roams in Japan, at £9 for 30 days on its Data Roaming Bolt On Zone 2 (1GB) option (checked 26 October 2026). A travel eSIM gives you local data there instead, while your O2 number stays active for calls and texts.
For data, the eSIM. O2's 30-day option is £9; a Slashtel eSIM with 3GB for 30 days is $4.69 (about £3.51). O2's option also includes calls, which the eSIM does not.
Yes. The eSIM is added alongside your O2 SIM, so your number stays in the phone for calls and texts such as bank codes. Set the eSIM as the line for mobile data and turn data roaming off on the O2 line. Whether O2 charges for anything you receive abroad depends on your plan, so check with O2 before you travel.
No. It is data only, with no phone number. You can call on WhatsApp, FaceTime or similar apps over the eSIM data.
Most iPhones from the XS onwards, Google Pixel 3 and later, and recent Samsung Galaxy S, Z and A models, provided the phone is not carrier-locked. Check under Settings for an option to add an eSIM.
Install it at home before you fly, while you have Wi-Fi, and switch mobile data to it when you land.