Who I have the same questioned this topic

I am traveling to Germany in several days for several months. I have signed up for the montly travel plan. Can I call someone in the US from my contacts, or do I have to manually enter the + and the country code? I will have wifi. If I enable wifi calling will I still be charged for minutes? I have seen some people say that they have been charged. Does switching off data and turning on airplane mode affect these things? Lastly, does anyone know, once I land In Germany, what do I have to do to my phone, so that It will work.? I am assuming my sim card is fine through verizon.