Will not work at internet cafes overseas

I have Vonage as my home/office phone service and it has worked fairly well over the past four years. I just purchased the V-Phone specifically to make calls while I'm overseas. While in Ukraine, I went to four different internet cafes, and the V-Phone would not work on any of them. Vonage indicated that this is probably because of the firewalls at the cafes. Regardless of why, the bottom line is that the V-Phone is only functional when used with networks without firewalls, which pretty much makes it useless at most internet cafes. I was able to use it on my laptop at two different places that had unsecured wireless networks. A guy sitting next to me at one of the cafes was using Skype, and he had no problems. Apparently Skype uses different technology than V-Phone, so maybe this is the way to go. I am disappointed that V-Phone does not work "as advertised", and their technical service was of little help on this subject.