We just spent four weeks in several European countries. We paid $50 for a Travel Sim from Australia post. This gave us $25 credit which we topped up by another $25. Top up is simple too. We came home with around $18 still on it & that included several calls to Broncos11 for World Cup Cricket reports. Cricket's not big in Europe
It's easy to use as you just insert the card, turn off your regular package, turn off roaming & away you go. When we went from one country to another, it automatically switched to the country we were in. With Telstra, if your phone is locked (depending on your package), there may be a fee to unlock it so the sim will work. We took my 6 year old Android & had no problems. You are advised of your credit each time you phone a number. There is a bit of a time delay so you can talk over each other at the start.
Remember to put the Oz phone code in front of any numbers you wish to ring & remove it from those numbers when back home as they won't work here, as I found out
Make sure you have "Roaming" disabled & Bob's your Uncle.
It's good for twelve months & longer if I use it here & top it up which means, if I go away next year, I just whack it in & away I go!
Wifi was freely available.
Have a good trip.
Steve