Download OG Whatsapp
1. First take the full backup for your messages and data before going through OG Whatsapp:
2. Clear whatsApp data:
3. Go to /sdcard/WhatsApp folder and rename it to /sdcard/OGWhatsAp:
4. Uninstall Official WhatsApp
5. Install OGWhatsApp
6. It will ask for your number. Give the old number which you have installed in official Whatsapp earlier.
7. Click OK