Costa Rica May Criminalize VoIP
For amateur radio operators in the US, it's illegal to receive or transmit international messages for a third party unless there exists an agreement between the US and the other country specifically allowing it. This includes patching (allowing a foreign operator to connect to a local US telephone network through your station).
The reason is precisely as you stated - some governments do not wish to allow any mode of international communication which would compete with the established system (which they own or have a significant interest in). Kind of sucks for VoIP, but is nice for amateur radio because you don't have a whole bunch of people with no interest in proper radio operation simply using it as a way to get around telephone toll charges.
I think the US regulations are different from those of the parent poster's country in that they generally apply only to third-party messages. Licensed amateur operators are allowed to have international conversations with other licensed amateurs without formal restriction.