It's a biggie if, like Vodaphone in Prague, the customer service staff have no idea what they're doing. I had to throw the Vodaphone SIM away and go with T-Mobile instead. No problems then, just as I had no problems with A1 in Austria.I've also used my Verizon Note 2 without root in several foreign countries. All I had to do was to buy prepaid GSM sim cards from supermarkets or hotel front desks. However, it's necessary to enter the APN setting on some GSM carriers. (no biggie, since it usually comes on a piece of paper with the SIM card, or available by calling the customer service number)