clearest international calling card

Question:

This is a serious questions.I hope you can help me.

I have tried Tele3, Rebtel, Yespinless, and a couple of others.

which calling card is the clearest international calling card to call from USA to Chile.

My suggestion:

All of these have been terrible! Sometimes I can’t get through, she can’t hear me, I can’t hear her.

Tele3, Rebtel, Yespinless are small, you should choose big one.such as comfi calling card ,spyeed.THese are you right choice.