There are several methods you can use to disable WhatsApp from your phone. We’ll go through them now.
Sign in from another device
WhatsApp can only be active on one phone number. If you ask for a duplicate SIM card and insert it into another device and confirm your number, the session you started on the phone you just lost should be closed (thereby disabling access to your calls on that phone will).
If you go to your operator’s store, ask them to erase your previous SIM card (if it’s allowed) and then ask for a duplicate of it. Normally the duplicate of the card can be made immediately in the store, while if requested by phone it may take a few days to arrive in the mail.
Wipe all phone data remotely
Another option is to remotely erase all the data on your cell phone. To do this, you go to a PC and type Find my phone in the address line of the browser. You will land on this screen where you need to select your device:
Find my phone main view
Google will then ask you for your account password to verify that you are the legitimate owner of your account. You will be taken to the next screen where you will click the option Consider erasing your phone), click:
Remote control options on the phone
A screen will then appear informing you of all the consequences of this action. After that you have to get up Yes, erase click and let Google do the rest:
Remote control button to erase the phone
Contact WhatsApp support
The last option we recommend is this one. The people responsible for the application claim on their website that in order to deactivate your account, you send them an email to firstname.lastname@example.org with the subject Stolen / lost phone: please deactivate my account (Stolen/Lost Phone: Please deactivate my account) should write. In the text of the message you must repeat the subject and enter your mobile phone number in international format. That is, your phone number with the country code in front. For example, if you live in Germany and your phone number is 0172 111 222 333, the email should be +49172111222333.