I'm going to be in London for a couple days next month on my way back home to America from Eastern Europe. I’m obviously going to have my smartphone with me, but am going to take out my SIM card out so that my telephone carrier doesn’t “accidently” charge me any roaming or internet costs. But, can I still partially use my smartphone if I take out the SIM card? Be prepared for stupid questions: Can I turn on my smartphone after I take out the SIM card??? I would test it now, but it is a pain in the butt to open up the back of my phone and take out the SIM card. If the answer is yes, I am guessing that I can still use functions on my phone that don’t require internet access like my camera and my calendar... If I download app’s like a tube map and street map of London, can I open them when the SIM card isn’t in my phone? Of course, that is assuming that I can find an app that doesn’t require me to access the internet (any suggestions?). If I go to a Starbucks or another free place with free wi-fi, will I have any problem accessing that wi-fi when the SIM card has been pulled out of my phone? Thanks for entertaining my dumb questions?? Any other thoughtful tips or comments on using a phone without a SIM card are welcomed!!!