Unlock iPhone 4s

Hi, I have my iphone 4s and I'm going to Italy at some point in the next year or so. I was hoping to be able to fully use my phone while there. Also, I travel to "the middle of nowhere" here in the U.S quite a bit and cell service is scarce. I was looking at Unlocking it and getting a local sim card while there. So, I was wondering if that would be a good idea for my situation and if not, what would be a better thing to do? And, how much does each option cost? Thanks so much for your time!!

~Applegirl2020