Network provider lock-sim locked

Only the carrier it is locked to can unlock it.

The ONLY source for unlocked iPhones in the US is directly from Apple. Devices from other retailers will be carrier locked.

You'll have to deal with the carrier the phone is locked to directly. You bought a carrier locked phone, which was not a good purchase. ONLY the carrier a phone is locked to can unlock it. You'll have find out what their requirement is to unlock the phone and if you qualify, which will likely involve paying a fee to them if they will even consider that.

Apple, nor anyone on this forum can help you. This is why it is generally not recommended to buy your phone in a country you don't live or will use the phone.