I have an iPhone 5 in the US on Verizon's network. My understanding is that my Verizon iPhone is unlocked and I can thus use my phone overseas with another SIM card. I am going to be traveling to Scotland for ~5 months. What is my best option for being able to make a basic number of calls, texts and have a limited amount of data? Ideally I would also be able to call the States if necessary, but I'm not sure if any plans allow for that. Thanks for your help!