Whatsapp contacts not Listed in Xiaomi Mi 3
The Xiaomi Mi 3 Smartphone runs on Android 4.3 Jelly Bean while the WhatsApp Android application requires only Android 2.1 and higher. So, supposedly, there should be no problem because you have a really supported Android operating system. Also remember that, when using WhatsApp, your entire free usage is only valid for the initial year or for only 1 year.
Beyond the first year and you still want to use WhatsApp you need to pay the annual subscription fee of US$0.99 per year. So, try to remember when you first used WhatsApp. If it’s more than 1 year already since you first used it, I think paying the subscription fee might fix the problem.
You may also try downloading the latest version in case you haven’t updated yet. Visit WhatsApp for Android to download WhatsApp 2.11.444. The developer also recommends that you have an unlimited data plan.