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Help USSD Codes not working abroad on KT (KT Telecom) Carrier S22 phone

YES i contacted them and they said that the problem is with the device
Same for me, the providers always say the problem is with the device.

A bit of research tells me that it could be because the phone you bought is registered with a certain provider and it doesn't support the frequency bands of the provider of the USIM you want to use.

In my case, the phone can call, send/receive messages, but USSDs don't work at all.

I have no idea until now how to solve this problem. Maybe next time, I should buy an unlocked phone (that is, I shouldn't buy a phone through a service provider)
 
Sounds like you're sending the wrong code, and your carrier isn't recognising it. USSDs(Unstructured Supplementary Service Codes) are carrier specific. Sometimes used for things like checking your account airtime credit balance, e.g. USSD "*101#" is for account balance enquiry with China Unicom. Check with your carrier for what codes they use.
I am using the right codes for my carrier, but it still doesn't work. The thing is this phone that I have was bought from a different carrier abroad. I am in a foreign country now, and the phone would not work with USSD codes. It can still call, send and receive messages though. What should I do?
 
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Why do you need these codes? What are you trying to do?
USSD codes is part of life where I live. Starting from paying for prepaid services, banking and paying my bills. My phone was under the KT (Korea Telecom) carrier, and I brought it with me abroad. Sadly, I find out that phones bought through the KT carrier company does not support USSD in foreign countries. The phone doesn't look locked like how different carrier sim cards are locked in the US, where you need a unlock pin code.

My phone can call and receive messages with the local USIM but the only problem is when I type in the USSD code, it refuses.
 
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USSD codes is part of life where I live. Starting from paying for prepaid services, banking and paying my bills. My phone was under the KT (Korea Telecom) carrier, and I brought it with me abroad. Sadly, I find out that phones bought through the KT carrier company does not support USSD in foreign countries. The phone doesn't look locked like how different carrier sim cards are locked in the US, where you need a unlock pin code.

My phone can call and receive messages with the local USIM but the only problem is when I type in the USSD code, it refuses.
*when I type in USSD codes* (ommit "the USSD Code")
 
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USSD codes is part of life where I live. Starting from paying for prepaid services, banking and paying my bills. My phone was under the KT (KT Telecom) carrier, and I brought it with me abroad. Sadly, I find out that phones bought through the KT carrier company does not support USSD in foreign countries. The phone doesn't look locked like how different carrier sim cards are locked in the US, where you need a unlock pin code.

My phone can call and receive messages with the local USIM but the only problem is when I type in the USSD code, it refuses.

I read online that it might have to do with whether or not the KT Telecom Carrier supports the frequency bands that my local carrier provides? Is this valid? What should I do then? Some people say, I should give up and just buy another phone that is unlocked or is without any carrier. But I can't go back now and buy another phone! Please help~
 
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USSD codes is part of life where I live. Starting from paying for prepaid services, banking and paying my bills. My phone was under the KT (KT Telecom) carrier, and I brought it with me abroad. Sadly, I find out that phones bought through the KT carrier company does not support USSD in foreign countries. The phone doesn't look locked like how different carrier sim cards are locked in the US, where you need a unlock pin code.

My phone can call and receive messages with the local USIM but the only problem is when I type in the USSD code, it refuses.

I read online that it might have to do with whether or not the KT Telecom Carrier supports the frequency bands that my local carrier provides? Is this valid? What should I do then? Some people say, I should give up and just buy another phone that is unlocked or is without any carrier. But I can't go back now and buy another phone! Please help~

Those USSD codes are carrier specific, and they won't work when you're international roaming with a different carrier in another country. Really the only thing you can do is find an alternative way of doing the payments, etc, like using the carrier website, if that's an option. And AFAIK changing your phone will NOT make it work.
 
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Those USSD codes are carrier specific, and they won't work when you're international roaming with a different carrier in another country. Really the only thing you can do is find an alternative way of doing the payments, etc, like using the carrier website, if that's an option. And AFAIK changing your phone will NOT make it work.
I am not roaming. I am using the local USIM simcard on my phone. I am using the right USSD for the Carrier in the country that I am living in. It seems like there is some kind of LOCK on my phone regarding USSDs. I don't know how I can get rid of this LOCK. The phone can still call and do messages though.
 
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I am not roaming. I am using the local USIM simcard on my phone. I am using the right USSD for the Carrier in the country that I am living in. It seems like there is some kind of LOCK on my phone regarding USSDs. I don't know how I can get rid of this LOCK. The phone can still call and do messages though.

Your problem is something I've not heard of before, but then I've never heard of a system that uses USSDs for making payments. Locks on phones will usually prevent the phone from making any calls or messages completely, like SIM-locks. Only thing I an suggest now is trying another phone, one that isn't "foreign".
 
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