I requested to u Unlocked carrier lock my iPhone 6

Carrier locks are entirely controlled by the carrier. You need to contact the carrier that owns the lock on your iPhone and ask them how to remove it. Go to Settings -> General -> About -> Carrier Lock to determine which carrier you need to contact.

Carriers are the companies that provide you cellular service. If your iPhone has displayed the message shown above, then you need to find out who the phone is locked to. If you just purchased the phone from someone, ask them.

I have the same problem, I have got the iPhone from my friend. I sent to her the iPhone barcode and she asked carrier, but they said they don’t have anything with that phone anymore. I do not know what to do

You need to contact the carrier the phone is locked to and ask them to unlock it, no one else can.

I'm having a same issue but in about option in iphone the Carrier lock option is not available And who are the carriers