Nothing is free in US. Free minutes they offer is targeted to long term benefit. Compared to the free minuted they offer, per minute charge in lot more then expected. However, their quality cant be beaten by calling cards.
I have been using kantipur tel pinless card . VISIT www.kantipurtel.com. They offer 7cents per minutes to ktm and 15 cents out side valley and the great is service. I wont say the voice quality is great but its far more better then we receive from calling cards. I tried once and stick to it since 3 months. No connection fee, no weekly fee, pinless dial, and much more.
Good luck