It's quite easy to permanently delete your account
You can do this from within the app itself
Ever get that feeling where you're just tired of all the spam you get on WhatsApp and want to remove the app once and for all? That won't solve the spam problem though. Whenever you reinstall WhatsApp, all the groups will be back and the spam will return.
If you leave those WhatsApp groups, people will often just add you back right away and the cycle resumes. A better idea could be to use other apps to keep in touch with those you care about and then permanently delete WhatsApp account. It might seem drastic, but cutting out WhatsApp isn't the end of the world. If that's what you want to do, here's how to delete your WhatsApp account. Follow these steps.
This will permanently delete your WhatsApp account, whether you use WhatsApp on iPhone, Android, Windows Phone or other devices. All WhatsApp data will be removed from your phone and if you've taken a backup of WhatsApp data, that will be deleted too. If you try and create a new WhatsApp account with the same phone number, none of the old data will be available - all your old groups, messages, and so on, will be gone for good.