what apps enable making a phone call from an iPad Mini w 3g, and what charges are associated with making voice calls?

I'm wondering whether I could get away with not having an iPhone (which I don't like using for much besides making voice calls, since the screen is so small) and just use an iPad mini for calls and more.

But I don't want to do this if using it for voice calls is exorbitantly expensive.

Thanks for sharing your experience and insight on this.

iPad

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