If you’ve come across a Samsung Galaxy S10 with a second logo on the back that reads Docomo, you’re not alone. These phones are quite popular on the secondhand market, especially outside of Japan. But what’s the deal with them—and are there any quirks you should know about?
What Is Docomo?
Docomo is one of Japan’s largest mobile network carriers—so big, in fact, that Samsung allows them to put their logo on the phones they distribute. Alongside the branding, these phones come with Docomo-specific firmware and pre-installed apps.
You might think that would limit them to the Japanese market, but surprisingly, you can find these phones worldwide—often for a bargain.
Why Are These Phones So Cheap?
Used Japanese phones often get sold in bulk through auctions. Small shops or individual resellers will import them and sell them locally at affordable prices. Many are network-unlocked, meaning you can pop in your local SIM card and start using them like any other Android phone.
No flashing, no rooting—just plug and play.
Well, mostly.
The Catch: International Dial Assist
There’s one small quirk with these Japanese firmware phones: a pop-up that appears whenever you try to make a phone call. It’s called International Dial Assist, and it gives you two options:
Call to Japan
Call without country code
You’ll want to choose the second option every time, or else it might mess with your dialing.
Why does this happen? The phone’s firmware is still set up to assume it’s operating in Japan. So when it sees a local number that’s not in international format (i.e., starting with a “+” and country code), it thinks you’re trying to make an international call—and tries to “help.”
Can You Turn Off This Pop-Up?
Yes, and here’s how.
First, you might see outdated advice online suggesting you go into your system apps and disable something called Call Settings. While you can force-stop it, on many phones, you can’t actually disable it—and even if you could, it won’t solve the issue.
Here’s the real fix:
Open the Phone app (whether it’s the Samsung dialer, Google dialer, or a Docomo variant).
Tap the three-dot menu (often in the middle or top right).
Go to Settings > Other Call Settings.
Find and tap on Assist International Calls.
Turn it off.
You can also manually change the country code to match your current region, but disabling the feature altogether is the cleanest solution. Once you do this, your calls will go through without the pop-up. No fuss.
Will It Affect Anything Else?
Not at all. Disabling International Dial Assist won’t stop calls, texts, or data from working. It’s just a minor assist feature, not a core component of the phone’s functionality.
A Note on Sony Phones
Quick side note—if you’re dealing with a Sony phone from Japan, it’s a bit trickier. Sony still releases new models in Japan that never make it to international markets. These often require you to reflash the modem firmware to get full support for local LTE or 5G bands.
They’ll work out of the box, but you might have limited connectivity unless you do the extra work.
Final Thoughts
Buying a Japanese phone like the Samsung S10 from Docomo can be a great way to save money. They’re fully functional, unlocked, and often in good condition. Just be aware of the few quirks, like the International Dial Assist feature—but as you can see, it’s an easy fix.
If you’re tech-savvy or just want a solid phone on a budget, these imports are definitely worth a look.