I have Google Voice on my Android (4.0.4 Samsung Galaxy S3) and it is set to make all calls using GV (cause I want the user to see GV number on the caller ID). However I encounter this problem: the number that appears on my mobile phone (when dialing out using GV) is some unknown (random?) number, not the number that I'm calling. Say I'm calling 212-333-4444 it shows 617-234-1234. It is in fact calling the right number but what shows is the number that GV is using. The problem is that when I look at the log I can't see who was called nor can I try to recall that number.
It appears this is a bug with the S3 phone.apk. The XDA thread doesn't have a solution, but there are some things to try...I just don't know if they'll actually fix the issue. You could try installing a replacement dialer. If you're rooted, you could try finding an alternative phone.apk (perhaps from the S2). Finally, a custom ROM built on AOSP (like Cyanogenmod) may not have this issue.