Speed of light in glass is about 2/3c. Internet routing does not follow great circle routes either, so add an extra 20% fudge factor for that.
From experience, voice calls sometimes get extra latency added in for no good reason whatsoever. Calling again usually resolves the issue.
So while there's a bit more delay, despite being noticeable it doesn't change how you talk on the phone.
*OH~2~