How to use existing Whatsapp account on new mobile with new SIM? I could not use my existing whatsapp account because My mobile have been stolen. I bought new mobile and new SIM as well, now I want to configure my existing whatsapp account on new Mobile with another SIM number. Can anyone please help me?
You cannot use your old Whatsapp account with new sim when you don't have access to your old number.  

All you can do is to contact your network provider and explain the situation, submit documents and request a new sim with the old number. Once you get your old number back, you can either choose to use whatsapp account with it or shift the account to new number.   

Shifting Whatsapp account to new number maintains the old account's whatsapp groups, account info, settings. You still have to share your new number with your contacts so they know its you and update their address list.  

To shift the WhatsApp account from old number to new number, login whatsapp with old number and open Settings >> Account >> Change number .