I'm a chilean and I work in a company that develope network services for Movistar and EntelPCS.
It's true that Movistar has a restriction for international calls in the 3 first months since sim's activation. EntelPCS hasn't that restriction and you could make international calls inmediatly.
I think that EntelPCS has a better voice service than Movistar, but Movistar has greater coverage. Anyway, both have good coverage in major cities and towns.
I think that Movistar has that restriction to avoid tourist buy prepaid sims and they had to use roaming that report Movistar more money.
(sorry for my bad english
)