2 mobile, 2 sim, 2whatsapp account I have 2 mobile old lenevo with Vodafone sim
 A6000 and new MI note4 with Jio sim.
Both mobile is having different WhatsApp account. I want to use old mobile WhatsApp account with new mobile and vice-versa. Now if I want to exchange my sim card what should I do? WhatsApp is not having logout option.
Once I uninstalled WhatsApp exchanged sim and again reinstalled WhatsApp. But it's not performing well. Groups appears in old Lenovo mobile and individual friends appears in new MI note 4.
Mobile number changing in WhatsApp : 


Open WhatsApp > goto Settings > Account > Change number.

[ currently, backup both your whatsapp accounts to google drive. Then change number on both phones or clear data on phone. Again open whatsapp, and set the things, restore from backup. Now, you can have all the chats and groups from lenovo to mi device and all items to mi to old device.]


WhatsApp Logout: 


Only web version of Whatsapp has logout option. In android, you need to clear data before uninstalling Whatsapp. Also, delete whatsapp folder from internal storage.


Backup: :
You have option to backup your current whatsapp data using google drive. Goto whatsapp settings > chats > chat backup. Set email account in google drive settings and tap on backup.