Viber out Dropped Calls

[WPCentral Question]

Hi, I am currently studying abroad in Brasil and am trying to use viber to contact my family in the US. I bought credit for viber out and I also have a good wifi connection. Anytime that I call someone, the connection is great and it works perfect, but then the call just drops after about one minute of talking. It does this every time I call someone. Any ideas on whats going on would be great!!