I have a brazilian voip phone in the US. Everything was very good, but when I came back from Brazil last time, my router wasn't working. I call a technician and after 30 minutes was perfect, but not the VOIP. He told me that my internet provider changed the DNS and for some reason I could not access the site www.falevono.com.br.
I already call the internet provider and the answer is that the problem was in Brazil. In my iphone it is working if I'm not in my wireless connection.
I can't change the internet provider because in my area I dont have more options. So, I think I can try to configure my router (airport extreme) in a different way. Can someone help me?