Because it can be used from a mobile or cellular phone, work, home, and pay phones, you'll find you won't need any other phone cards to call USA. Mobile Caller works through traditional phone calls, and is not dependant on the internet quality, so you're guaranteed the clearest calls to USA.
NOTE: Rates to Cell Phones are higher than advertised landline rates, due to different cell carriers. Application of surcharges
and fees will have the effect of reducing total minutes actually received on the card from the minutes announced.