Swipe up from the bottom of the screen to bring up the control centre. Is the crescent Moon button illuminated? If it is, the Do Not Disrurb feature is turned on and callers won't get through to you. Turn it off by tapping it and see if that helps.Why are callers being told that my iPhone is turned off? It is on and I can make calls, but I cannot receive calls.
In regards to Genius Bar appointments, I bought my iPhone in Canada and had no trouble getting a Genius Bar appointment and a repair while on vacation in the United States. It wouldn't hurt to ask, just in case you need service in the future.I do not believe I can get a genius Bar appointment at an Apple Store because I bought my phone in one country and am using it in another. Wouldn't the iPhone's warranty only work in the country in which the iPhone was purchased?
I do not believe the issue is with the wireless carrier because my SIM card works fine in another phone, and another SIM card that works in another phone does not work when placed in my iPhone.