Thank you, mplevy!
I'm a little slow with the phone lingo, but I think I get what you're saying.
So, if Spain has CDMA850/1900 or LTE 750 network, I could get my phone to work with the existing card, if a carrier were to activate it? And, I cannot put any other card in my SIM slot.
I think I got it.
So, another question for those out there, is it easy to sell my used Thunderbolt?