I want to unlock the carrier

jio wrote:

 

 

So basically you can't unlock the phone. Never buy a phone from the USA without it being carrier unlocked since all phones are sold locked from Tmobile.

But I am korean

how to be a customer of Tmobile USA?

You need to be a customer of Tmobile USA and meet the requirements in the link below to unlock the phone.

https://www.t-mobile.com/responsibility/consumer-info/policies/sim-unlock-policy

To be eligible.for a SIM unlock from T-Mobile USA.  You must be a T-Mobile USA customer, you must be the original owner of the device, and you and the device must meet all of the SIM Unlock Policy requirements. 

https://www.t-mobile.com/responsibility/consumer-info/policies/sim-unlock-policy