Ironically, you've got a better chance of getting acceptable quality on mobile-to-mobile calls these days than when calling from a landline:

The big mobile carriers actually have VoIP interconnects preserving wideband audio, while connecting to an (especially smaller) landline carrier might still involve a circuit switched path (going to the physical location of the area code dialed, too!) that inevitably forces everything through a 4 kHz, 8 bit bottleneck.