I think is a simply question of anti-spam configuration security,a lot of Spammer Bot from Russia attack forums especially if users posts cooments with works like "works" ," Business" ,etc i had and i Administrate some forums and the only way to reach this attacks is Ban IPS from this countries unluckily ,use a proxy server is the solution.
I now use Skype to call the US and Japan on a regular basis. It costs pennies and the connection are excellent. I highly recommend it to anyone that has to make international calls.