This is a member of the Viber R&D Team!
We have received various similar complaints from Viber users in your area of the world, and we have investigated this issue. It seems that the outgoing access to Viber and VoIP applications may have been blocked by your specific service provider [generally, this block is only on basic package plans].
Please check with your carrier, Viber will not be able to bypass your carrier's network blockage. It is in your carrier’s or country's decision which applications they wish to allow or block network connections to.
If you have any question about Viber - please feel free to ask.
An official representative of Viber Media (Viber app.)