You can't hack it into an iPhone itself but you can get two things that allow you to make calls (over WiFi) and text (over WiFi). If you go here
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That will show you how to make calls. As for texting simply go into the app store, or installous and search text and a bunch of free and paid apps for texting will popup (use installous so you can use the paid ones and have no ads in the app).
Hope this helped.