I'm from the United States, and I currently have an iPhone 4s on the Sprint network. In late September (2013), I'll be flying to the UK for a year of studying abroad at Oxford University until June (2014). My Sprint contract expires towards the end of October 2013. I'd like to use my iPhone in the UK instead of getting a new phone, so here are my questions:
Can I use my current American iPhone on a UK phone network?
If so, what UK phone network would be the best choice for a short-term (aprox 9 month) plan?
What is my best bet (web service, phone apps, calling plan, etc.) for making international voice calls back to the US?