Hi Percival, if you got this phone from a carrier it might still have carrier lock restrictions on it, and that is why you can't use it with any other networks. Before you can do that, you need to have it unlocked, and based on what you've said it looks like you may have to take it to your original carrier for them to unlock it for you. I'm sure that they can give you some answers if you get in touch with them with your questions. Hope this helps!