Bolivia's national phone company Entel has outlets on practically every block in major cities. Most Punto Entel shops also have internet-connected PCs, typically Bs4/hr.
While traditional payphones still exist, you can also make local calls for Bs1 from cellular phones at kiosks or "walking phone booths" - look for a guy in a green vest with a cellphone on a chain.
If you are staying for a while, consider buying SIM cards for your cellphones. They are quite cheap and you get good network coverage in all main cities and towns.