What happens when you delete your WhatsApp account
Press and hold the WhatsApp icon on your iPhone Home Screen until it starts to wiggle. Now tap the small x-shaped symbol on the icon to delete the app. Do this after deleting your account as explained above.
Every other day, we hear from some sort of new messenger app that is the new kid on the block. Depending upon your contacts, you might go for Threema or Viber, Line or Joyn or even Skype. Note that Skype is not really the best choice in terms of privacy and secrecy. There is also an non-centralized app by the BitTorrent group called Bleep.