How can I delete iPhone contacts permanenlty before selling?

I want to delete all phone number from my iPhone 5 permanently before selling! As we all know,when we erase iPhone data by without restore to factory setting,it can't erase all data on iPhone permanently,even some professional iPhone data recovery can restore them.
Asked Aug 18, 2015
You want to compelely delete iPhone contacts, however there’s a professional iPhone contacts erase software you need to be cleared wholly. Take this guide will help you.
Answered Aug 18, 2015

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