Megafon for Mac

From Xnet Communications:

Xnet Communications, a maker of market leading Captain FTP, introduces new Telephony Software, specifically designed for the Mac.
This is no half-baked Apple Java-compatible program nor is it a port of any Windows or Linux version. This is a pure Mac implementation for Mac users only.
Therefore user experience is set on top of the powerful telephony engine.

Megafon is an easy to use Internet phone for Mac OS X providing crystal clear voice quality in an attractively sleek GUI interface. The quick one-step
configuration will allow you to get talking to other Megafon users in seconds. Simply dial the number of the person you wish to talk with or select them from
the Phonebook to dial their number. Create private telephone networks by using the option to add multiple SIP providers.