PhoneClub: best all around
PhoneClub has the best rates per minute (when last checked). They sent a notification when the rate increased for calls to a particular country. I appreciated their transparency. The option to purchase a low minimum Voice Credit for $2 makes it ideal for a household that calls overseas intermittently. You can access your call records and view balances as well, which I find upfront and legit. After physical phone cards became unavailable, I would pay for International add-on through my plan from time to time. The minimum purchase was $10 which was more than needed. Very glad to have discovered PhoneClub. They've helped us stay connected to an elderly relative overseas.