I am taking my first trip abroad to Germany at the end of July. (also possibly Czech Republic and Poland). What do I need to know when using my phone internationally? Can I use the phone I have (Iphone 8+). I will be staying with my son, so I will have access to his Wifi when at his home, but what do I need to know about using the phone there, receive or send messages there and to and from the US, and calling there as well as to/from the US. This is all new to me, and I don't even know what questions to ask, what I might need to purchase, etc.