I have a global data plan for my iphone 4, but i'm not getting 3G in amsterdam?

I can use Wi-Fi in the hostel, but I would like internet when I'm out running around and I need directions and stuff. I already switched my data roaming to on in my settings and all that, shouldn't it work? Yes I activated my plan changes before I left. Isn't a data plan supposed to cover 3G? The Verizon guy said it should but I think he lied to me.

WELL DON't KNOW MUCH ABOUT NETWORKING, BUT I THINK you SHOULD VISIT your NETWORKS WALK-IN CENTRE, AND IF THE CAN't FIX IT, THEN I Recommend U CHANGE THE PHONE TO HTC PRODUCT HANDSET. IF you WANT I WILL TELL you THE MODEL TO BUY AND HOW you WILL CONFIGURE IT TO PROVIDE U THE MAP DIRECTIONS, MAY BE FREE INTERNET BROWSING AND So ON AND So FORTH JUST LIKE I DO WITH MINE.