I am in Canada, and I use two cards. I have the same criteria as you do, so here are the cards I use:
VOX International-There are many types of VOX cards, but I think they all charge the same per minute rate.
Nengda Tong Calling Card- Seems to have a good rate, and apparently it keeps a log of your calls, so you can get the call log when you are ready to process the immigration stuff.