My prepaid sim is not working
I bought the prepaid phone with AT&T and I got message about activation, and I made pay account in website where you guys sent a URL.
And I'm in South korea now. So I wanted change the sim card with korean sim card. and I tried to change at Korean mobile shop, but It was failed. so I just put US sim card again. But It's not working. when I call, the device shows up that my phone is not resistered on network. I did networking reset, turning on/off, putting sim card again, updating software. But It's still not working.
Is this a physical sim card problem? Do I need to change the Sim card? I wanna keep my US number.