Straight talk has been using 18 t's Network for quite a while, and I ended up connecting it with straight talk, and it absolutely worked and it worked great.
How To Unlock at&t iPhone 5 For Any Carrier | Unlock AT&T Phone or Tablet - ATT
This is about how to unlock at&t iPhone 5 for any carrier, To begin with, the unlocking process, we first have to get the IMEI number, which can identify which phone need to unlock, when making activation, need to select the correct service provider, and will receive the email after done.
To begin with the unlocking process, we first have to go to the dial pad of the iPhone, and get the IMEI number, and to do this, you got a dial-in star pound zero six pound, once you do this, new screen will come up showing you 15 digit IMEI number, based on this number, we can know exactly which phone needs to be unlocked and request an activation through Apple server. So once you have this IMEI number, please make sure to save it somewhere, write it down exactly as it appears on the phone. Don't make any mistakes, because this number is very important.
Once you have this number, I'm just going to take the SIM card out, and as you see I have here an 18 two SIM card, and I'm going to put inside this phone at t-mobile SIM card, as I promised, let's give the SIM card into the phone, and let's put this in, and as you can see, once I'm putting in the t-mobile SIM card, the phone itself is locked, and it will say activation required, because this phone is still not unlocked and in this case it requires you to make activation through Apple server.
If your phone is unlocked, it will let you do the activation completely, so once you get to this screen, I'm basically going to go to this website, which is called iPhone OS unlock.com, WWW.own.OS.unlock.com, so once we get to this website, you will notice here a section at the home page, where you can actually enter the information of your phone.
For the onion number, I'm going to go ahead and enter that in your number that we just received from the phone, this model is an iPhone 5s, so this is what I'm going to choose, and the network of this iPhone is 18t, this phone has been purchased from 18 to the United States, and it is locked to 18 to the United States, and it's very important to select the correct service provider your phone is from, so I'm going to select this, and just in this case you'd have to go and complete your order, I've already done this, and I received their results in my email is now unlocked, and it's ready to go on VI.com.
You just have to open iTunes which is I have, it open over here already, and take you be cable, here is the USB cable, I'm just going to connect this USB cable with the iPhone, in this case, remember we have the t-mobile SIM card in this phone, now it doesn't matter what SIM card you have in this phone, as long as it's a different SIM card from the original provider, so in this case what we have to do is just connect the USB cable to the iPhone, and once it's connected to the computer, we can continue with our activation. So I'm going to just let it use, that's it, as you can see it's connected, it already has done the activation through iTunes.