Motorola

I have a new Verizon Motorola V325 tri-band phone which I'm happy with. The voice quality is normally fine, although to the critical ear it's obviously digitized. Every so often, however, the caller sounds even more so, bordering on garbled but still understandable. Two calls in particular come to mind, one from a satellite phone and another from the UK. I assume my phone is fine because most calls are OK. I'm theorizing that the more digital hops a call has to go through the more the voice is processed and reprocessed, and the less smooth (analog like) it becomes?? What are the various factors that effect the call quality? Thanks