I m traveling to the UK for my first time and was wondering what I should do for communication?

I live in the US and I have an iphone 6 and do service with Sprint. I would like to be able to communicate when I m in London and text or call locally. I am planning on keeping that to a minimum and I m looking into some payphones and was wondering what I could use for a payphone and how could I get one? I was also told about the app, Viber and I could use that on my phone and not have to get a phone in the UK. I am however, concerned about using viber because wouldn t I be charged data roaming and how would it work if I had my data off and no wifi? Also, if I got a UK sim card for my phone, wouldn t I loose the information I already have in my phone? If I do get a prepaid phone, who should I get it from and could I get it shipped to the US?

Your advise is appreciated… Thank you.

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